It is almost certain that low expectations lead to low results. Likewise, most often high expectations lead to high results.
High expectations are great because they produce high achieving. The problem with them, however, is they inevitably lead to disappointment because every once in a while we let ourselves down.
It might be better to have no expectations. (Very zen-like, I know.) Perhaps working hard and accepting what happens is a better way of approaching one’s day.
I think this philosophy works well in all areas of life. Do your work, and let the chips fall where they may.