Apparently, a very simple question, but found to be most pertinently experienced in day trading. More broadly, I may put it that the basic issue is rather you earn early on in the day and lose it or make a net loss, by the end of day. Flg few reasons come to my mind
One is rather more cautious and trade in moderate quantities and book out profit rather early to build a profit base for day. As the day progresses, there is a tendency to trade aggressively in terms no trades, trade qty and level of profit booking. and rather adventurously once early few trades are succesfully.
There is a tendency to trade in the same direction of successful trades. Whereas, markrt if not highly bulish,has tendency to book profit in couple of hours and as such brings prices down. generally we are trapped.
After initial Teji sentimebt, a volatile markket may give sharp jolt causing
loss booking in positions.
In short,in retrospect it looks that it would have been better, to have earned a tidy profit in early hours and retain it by notlosing further, to avoide possibility of losing profit in later trends