To rectify a damaged relationship. After Jill heard that her father had become ill, she decided it was time for them to mend their fences before it was too late. The politician tried to mend his fences with his constituents after the scandal, but was not able to regain their trust before the next election.

To start behaving in a different, usually preferable, way. After I got in yet another fight at school, the headmaster told me that I had to mend my ways or else I'd be expelled. No matter how old you are, there is still time to mend your ways.

old-fashioned To begin moving faster, especially to meet the speed of another person. Noticing me behind him, the man mended his pace, and I mended mine, until we both began running through the crowded alleyways.