Eben Mishkin

Your MC is a time traveler but the way time travel works only allows a person to exist in any given moment up to four times before the travel possibility collapses barring them from ever returning. This means your MC can travel back to any moment in their own lifetime a maximum of three times to try and change or fix something. After the third time they're stuck with whatever they did last. This last trip your MC made left things worse instead of better.