I slept with my supervisor last year
Why did you sleep with your supervisor?
I did it because she is beautiful and I can't resist beautiful women.
It is unwise to get romantically involved with people you work with, especially if they are your supervisors. You should work on your self-control if you feel like you can't resist sleeping with beautiful women.
Her husband isn't around most of the time so why shouldn't I?
She is your supervisor so if anything goes wrong, she might choose to save herself over you. If she's also a married woman her husband might hurt you if he finds out what you did. It's better to break things off now and explain to her that it was a mistake.