How to keep success from leading to expectations

A common theme I see in athletes I work with is success leading to expectations, which develops into stress, resulting in them underperforming in games. But shouldn't success lead to more success? Shouldn't it generate high level feelings of confidence and trust, knowing they've done it before so they can do it again...yeah, sometimes. But other times success leads to fear and worry. They need to prove to themselves and others that it wasn't a fluke. That they can play like that again and a...