Calculating Your Probability of Success. Calculating your chances of winning by observing your opponents' moves and the cards in your hand is another aspect of knowing when torummy east drop. For example, it might be wise to withdraw to reduce your losses if you see that your opponent is about to declare "Rummy" and win the game. Everything Depends on Timing. Similar to this, it might be preferable to give up rather than play on with slim chances of winning if you have not been able to form any sets or runs after multiple turns.