Most gambler enjoy that because they enjoy the fun from gambling however they forget that they dont have unlimited bankroll to play so better stop when you already get profit. I dont think that controlling the goal will be the deciding factor, control what you are gambling for and that is the deciding factor
Have point, setting plan sometimes doesn't assure that we will win but it does help us to decide whether to continue or not , knowing the amount we can win can help to decide but if it goes along us,so setting yourself in reality is the key,you'll surely know if its your day or not.