Lost lessons.
I’ve lost jobs, friends, money, illusions, dogs, contests, self-confidence and relatives.
The lessons seem to be similar, regardless of the details.
If you wished you had done more, tried harder, reached out, do so going forward.
Own any responsibility and don’t repeat that behavior.
Take time to remember and revel in the good parts. There are always good parts.
Unexpected people show up, some you expected do, some you expected, do not. Appreciate the former, love the middle (rocks), and forgive the latter.
It’s the past. Learn. Make new relationships. You will make new mistakes.