In his book Eastern Wisdom for Western Minds, Victor M. Parachin tells a Japanese tale about how powerful our emotions can be, and how we must manage them, not vice versa. He writes:
A Japanese samurai warrior visited a Zen master, seeking answers to questions that had plagued him for some time.

"What is it you want to know?" asked the Zen master.

"Tell me, sir, do heaven and hell exist?"

"Ha!" laughed the Zen master in a contemptuous tone. "What makes you think you could understand such things? You are only an educated, brutish soldier. Don't waste my time with your ridiculous questions."

The samurai warrior froze in shock. No one spoke to a samurai that way. It meant instant death. Increasing the tension, the Zen master went on, "Are you too stupid to understand what I just said? Stop wasting my time and get out of here!" he shouted.

The samurai exploded with rage. As quick as lightening, his hand grabbed the sword, sweeping it over his head to get ready for the kill. In the split second before the sword descended to cut off the Zen master's head, the samurai heard him say, "This is the gate to hell."

Again, the samurai froze in astonishment. He got the message. It was his own rage that brought hell to him. The Zen master - as is customary among the greatest of Zen teachers - risked his life to make that fact inescapably clear. Pausing and then breathing deeply, the samurai replaced his sword. He bowed humbly, filled with respect and even awe.

"And this," smiled the Zen master, "is the gate to heaven."
This old story is all about moving out of emotional captivity. Many people are not the drivers of their emotions. They are driven by them; they are emotionally out of control. This is a significant personality weakness and a great danger. Uncontrolled anger and rage are major impediments to enlightenment.

Buddhism compares untamed emotions to a forest fire that roars through a person, consuming all that is good, noble, and virtuous. In Christianity, anger is cited as one of the seven "deadly" sins.

The Zen master is quite correct: an uncontrolled emotion is the gate to hell. The taming and directing of emotion is the gate to heaven.