Self-portrait by Cajal at his library in his thirties, from Beautiful Brain: The Drawings of Santiago Ramón y Cajal
We all like to think that we are talented enough to make a major impact on the world.

However, for whatever reason, no matter how intelligent or capable someone is they don't always get that big break.

Many people put it down to bad luck or not being in the right place at the right time, but there could be a scientific reason behind that lack of success.

Santiago Ramon y Cajal, widely considered the father of neuroscience, attempted to explore the psychological boundaries that prevented talented people from excelling in life.

In his 1897 book, Advice for a Young Investigator, the Spanish Pathologist detailed six different factors which restrain an individual's talents, which he called 'diseases of the will.'

1. Contemplators

First he details, contemplators. These people like to study the qualities of their chosen field and even master them but never feel any real need to apply them to a new situation.
[Contemplators] love the study of nature but only for its aesthetic qualities - the sublime spectacles, the beautiful forms, the splendid colors, and the graceful structures.
He adds.
[Contemplators] are as likable for their juvenile enthusiasm and piquant and winning speech as they are ineffective in making any real scientific progress.
Therefore, even if you are a master of your craft, its no good unless you are taking it in a unique or progressive direction.

2. Bibliophiles and Polyglots

Now those are two words which aren't too common anymore but can be easily defined as knowledge hoarding.

Absorbing tonnes of facts and figures about a variety of subjects might help you in a pub quiz, but this vain pursuit will not help you if you only want to project your knowledge.

Cajal explains.
Discussing everything - squandering and misusing their keen intellects - these indolent men of science ignore a very simple and very human fact... They seem only vaguely aware at best of the well-known platitude that erudition has very little value when it does not reflect the preparation and results of sustained personal achievement. All of the bibliophile's fondest hopes are concentrated on projecting an image of genius infused with culture. He never stops to think that only the most inspired effort can liberate the scholar from oblivion and injustice.
He then expands on this notion by saying that whatever we learn should be put to valuable use.
No one would deny the fact that he who knows and acts is the one who counts, not he who knows and falls asleep. We render a tribute of respect to those who add original work to a library, and withhold it from those who carry a library around in their head. If one is to become a mere phonograph, it is hardly worth the effort of complicating cerebral organization with study and reflection. Our neurons must be used for more substantial things. Not only to know but also to transform knowledge; not only to experience but also to construct.
So, while you might impress you're mates with your detailed understanding of obscure 1970s television, what good is it if nobody else can benefit?

3. Megalomaniacs

It's unlikely that many people would classify themselves as a megalomaniac, as they are usually people identified by they thirst for power and acknowledgement.

Yet, a megalomaniac is undeniably motivated and always want their talents to be recognised.

However, this desire and confidence can expose their biggest flaws, especially when trying to achieve something incredible.
As if believing in miracles, they want to start their careers with an extraordinary achievement.

They end up spending their lives planning and plotting, constructing and correcting, always submerged in feverish activity, always revising, hatching the great embryonic work-the outstanding, sweeping contribution. And, as the years go, by expectation fades, rivals whisper, and friends stretch their imaginations to justify the great man's silence.
Cajal also likens megalomania to dreamers, who always have grand ideas but never quite master their desired goal.
Their optimistic eyes see everything through rose-colored glasses. They are confident that, once accepted, fruits of their initiative will open broad horizons in science, and yield invaluable practical results as well. There is only one minor drawback, which is deplorable - none of their undertakings are ever completed.

The truth is that dreamers do not work hard enough; they lack perseverance.

4. Instrument Addicts

If you are obsessed with gadgets, apps or any particular tool, this one might be a bit too close to home.
Cajal writes that no matter your obsession or understanding of an instrument, you ultimately be useless if you can't appreciate its fundamental value.

He says:
This rather unimportant variety of ineffectualist can be recognized immediately by a sort of fetishistic worship of research instruments. They are as fascinated by the gleam of metal as the lark is with its own reflection in a mirror.
Cajal adds that this type of obsession is useless to other people if it doesn't aide them in their work.
Cold-hearted instrument addicts cannot make themselves useful. They suffer from an almost incurable disease, especially when it is associated (as it commonly is) with a distinctive moral condition that is rarely admitted - a selfish and disagreeable obsession with preventing others from working because they personally do not know how, or don't want, to work.
5. Misfit

Chances are that at some point in life, we have all felt like a misfit.

Maybe it was at school when you just didn't gel with the other kids, or maybe it was a job where your skills just failed to flourish like you would have hoped.

Regardless of the environment, feeling like a misfit can be damaging for talented individuals.

This can then lead to complacency and laziness, which never allows them to move beyond their current situation.
Instead of being abnormal, misfits are simply unfortunate individuals who have had work unsuited to their natural aptitudes imposed on them by adverse circumstances. When everything is said and done, however, these failures still fall in the category of abulics because they lack the energy to change their course, and in the end fail to reconcile calling and profession.
However, he does offer a solution.
They must generate the determination to reach for lofty goals, to seek an agreeable line of work - which suits their talents - that they can do well and to which they can devote a great deal of energy. Is there any branch of science that lacks at least one delightful oasis where one's intellect can find useful employment and complete satisfaction?
6. Theorists

Finally come the theorists.

This will apply to those thinkers and philosophers out there, who like to scrutinise every detail of their work to make it fit in with their agenda.

Although this level of research is laudable, it is essentially lazy as it is only developing their personal theory.
Basically, the theorist is a lazy person masquerading as a diligent one. He unconsciously obeys the law of minimum effort because it is easier to fashion a theory than to discover a phenomenon.
Whilst exploring hypothesis is encouraged, a rejection of facts is a dangerous pursuit according to Cajal.
Hypotheses come and go but data remain. Theories desert us, while data defend us. They are our true resources, our real estate, and our best pedigree. In the eternal shifting of things, only they will save us from the ravages of time and from the forgetfulness or injustice of men. To risk everything on the success of one idea is to forget that every fifteen or twenty years theories are replaced or revised
While you might not immediately associate yourself with any of these traits, Cajal's advice does remain informative and possibly highlights why talents often go to waste.

However, it should be noted that when Cajal wrote his teachings, his studies were only aimed at men.

When the book was published women were restricted from going to European universities and still couldn't vote.

Although this regressive line of thinking is thankfully no longer in existence, Cajal's findings still possibly ring true in the 21st century for both genders.