regret
express with regret
I regret to say that you did not gain admission to Harvard
decline formally or politely
I regret I can't come to the party
repent
rue
feel remorse for; feel sorry for; be contrite about
feel sad about the loss or absence of
sorrow
ruefulness
sadness associated with some wrong done or some disappointment
he drank to drown his sorrows
he wrote a note expressing his regret
to his rue, the error cost him the game