Suppose you're a day trader with $50K in your account. You have a couple of great trades and made $5K by noon. Would be it a good idea to lock in some of the profits by putting some of $5K aside and not re-investing it? Basically, you'd pretend that you only had $53K instead of $55K and trade only that amount. Many traders start with the same buying power every day so if you had a $5K profit at the close, the profit would be withdrawn anyway. But the difference is whether you put aside some of the profit in the middle of the day by "logically" withdrawing it from your account. Has anyone tried it? Do you see any downside to this?