On busy days
If you had a busy day and you cannot trade as long as usual, don’t begin to stress yourself. In this situation you won’t gain any advantage by trying to make your money in only half an hour. If you get nervous and don’t have much time left before you must leave your computer, your choices will reflect this.
You will get in a mood which doesn’t allow you to let trades grow. You probably will size up on your position in order to increase your gains. But what will happen is that you move back and forth between a few high volatile stocks and very probably lose money in doing that.
So try to be calm, if you trade. Don’t get into a hectic mood. If you don’t have much time to trade, better trade less and smaller positions, but in a wider range and just let them work (maybe with an active stop) while you are away.