In da BOX

Standing alone in a squared box..

will a man be able to say/do something that won't feel regret in the future ?!

reflection from (k)Snow Queen :
"He died because of me, and I said to him on the day he dies that if you are that kind of person, I won't want a friend like you. I didn't mean it, I shouldn't say that to him"

Should I say only nice words to people around me, so that I won't feel regret in the future ?