A dear friend of mine (she is married with kids) once told me that there should be no secrets in a serious relationship because once/if they come out, feelings can get hurt.

leomama, your partner was hiding something that you would have understood and wouldn't have judged him for. I think it indicates that your partner had some trust issues and he might have been hiding more things from you.

I think think there should be as little secrets in a relationship as possible because even a small uncovered secret can snowball into something big and nasty.