You might blame it on stress or time constraints.
But the fact of the matter is you could be worried about a lot of other things that prevent you from having mind-boggling sex.
Here are some common stress points:
I feel shy looking at him
If we're not in love, how can I enjoy sex?
What if he wants just sex and won't commit?
Don't orgasm that fast
What if contraceptives don't work?
What if I don't match up to his expectation?
I don't like the way I look
Prefer petting to intercourse
Sex has become boring. How do I tell him?
What will people say?