they do not know what they are doing, they have no idea what profit they want to take, sometimes they saw a stock goes up sharply after they kill their holding, next time they will expect the same, so they changed their original plan, they will hold a trade too long even the trade reaches their profit target, they expect more, then it turns into loss, then they will change their mind again, and on and on.... it seems they are manipulated by the market, no matter what they change, they just can not get it, the real problme is they abandon their trading plan easily, they have no rules, the market is endless, you must define a start and an end for a trade based on your timeframe style (to take 1 point gain in a swing trade is not a good trading practice, I find I just fit the minute to minute trading style, even though I know for example CROX short today, it will drop at least 3 points to 5 points in the day row, but I will have bad sleep or worry about sudden run -up becuase of some unexpecetd news, worrying about the position will cosume lots of my focus, I know I have this weakness and I can not conquer it, thus minute to minute trading style fits me). after you killed your trade within the desired profita range, you sould be proud of self, while not regret how much you missed. trading from this point of view is very boring, just routine work.
try to help those poor souls who did not get it yet!