Nicholas Darvas's Objectives and Weapons for milking money out of the stock market !

Darvas, after a series of random losses discovers his famous box trend following method but the question of when to get in and when to get out still haunts him - he writes :

And how to determine when to take profits?

I realized that I would not be able to sell at the top. Anyone who claims he can consistently do this is lying. If I sold while the stock was rising, it would be a pure guess, because I could not know how far an advance might carry. This would be no cleverer a guess than anticipating that "My Fair Lady" would end its run after 200 performances. You could also guess it would go off after 300 or 400 performances. Why did it not go off at any of these figures? Because the producer would be a fool to close the show when he sees the theater full every night. It is only when he starts to notice empty seats that he considers closing the show.
I carried the Broadway comparison through to the problem of selling. I would be a fool to sell a stock as long as it keeps advancing. When to sell then? Why, when the boxes started to go into reverse! When the pyramids started to tumble down­wards, that was the time to close the show and sell out. My trailing stop-loss, which I moved up behind the rising price of the stock, should take care of this automatically.
Having made these decisions, I then sat back and re-defined my objectives in the stock market:

1. Right stocks
2. Right timing
3. Small losses
4. Big profits

I examined my weapons:

1. Price and volume
2. Box theory
3. Automatic buy-order
4. Stop-loss sell-order

As to my basic strategy, I decided I would always do this: I would just jog along with an upward trend, trailing my stop-loss insurance behind me. As the trend continued, I would buy more. When the trend reversed? I would run like a thief.

I realized that there were a great many snags. There was bound to be a lot of guesswork in the operation. My estimate that I would be right half of the time could be optimistic. But at last I saw my problem more clearly than ever. I knew that I had to adopt a cold, unemotional attitude toward stocks; that I must not fall in love with them when they rose and I must not get angry when they fell; that there are no such animals as good or bad stocks. There are only rising and falling stocks—and I should hold the rising ones and sell those that fall.

I knew that to do this I had to achieve something much more difficult than anything before. I had to bring my emotions— fear, hope and greed—under complete control. I had no doubt that this would require a great amount of self-discipline, but I felt like a man who knew a room could be lit up and was fumbling for the switches.