Regret

They regret not taking the opportunity to travel abroad when they were younger.

The athlete had a regret that he didn't train enough for the competition.

His biggest regret was not spending more time with his family.

The singer expressed her regret for canceling the concert.

I have a deep regret that I didn't apologize to my friend.

The traveler had a regret that he didn't visit the historical site.

The patient expressed her regret that she didn't seek medical attention earlier.