Definition of set-up
A set-up is a frustrating situation that cannot be avoided. By set-up, we mean a "mise-en-scene". In short, you play a hand and the hand plays itself out, both for you and for villain. There are several set-up situations. One of them could be a set over set. One player opens 99. Another player 3-bets QQ. The player with 99 calls. The flop comes Q-9-2. Here, neither player can fold. Both are convinced they have the best hand. It is a set-up in the sense that the situation is inevitable. You have to take these situations with a good philosophy.
How to avoid set-ups?
The answer to that question is that it is almost impossible to avoid them. The good news is that the set-ups will go both ways. Sometimes you'll be the one losing your stack with the worst hand, but sometimes you'll be the one on the safe side with the best hand. Set-ups are not to be avoided. Set-ups are rare and every time they happen, none of the players involved in the hand can fold. If you have 55 on 5-5-7-7-x, you can't fold your hand because your opponent might have 77.