case 1: lets say u bought stock XXX at beginning of a rally at price RM1, u think price has topped  at RM2 after few days and quit so u took profit.

case 2: u keep holding XXX until it make higher highs and until end of rally. u sold at RM10. u didnt sold at rm2, 3, 4 because u think you would lose the "low entry cost".

for example is supermx/topglov recently. i could made 400% profit already but i quit too early.
then i reenter, reexit, again and again making my short term profit smaller than holding since beginning.