You find $100 on the street and hurry to put it in your pocket before someone takes it. Profit in a trade feels the same: it seems not really yours until you take it.
Example. Target — plus $20, stop — minus $10. Price reached plus $6, and you closed out of fear. If you do this every time, your profits will be $6 each and your losses $10 each. Do the math: with these numbers, even 6 right out of 10 gives a minus (6 × $6 = $36 of profit, 4 × $10 = $40 of loss).