Because my secret happened many many years ago... I do not mind
sharing. I fell in love with a married woman, some 12 years my
senior. Had a long and passionate affair, until we were found out
by her husband, who was 12 years her senior. Luckily, it coincided
with me having to leave Singapore for further studies. It was a
natural break for the both of us. She had her life and family to go
back to, and I had my future overseas to look forward to. It was
great during the affair (both of us did not regret it) and it was
sad at the end.
This was before I was married and my wife knows about this story...
so not really a "dirty" secret.