A pony who feels he has nothing left to live for confides with Twilight to do him a favor she absolutely refuses, which results in the desperate pony taking things to the extreme!
Lessons:
-You can never truly understand someone else's pain (what goes through their head)
-People can be loved, appreciated, and needed/wanted... but sometimes even these are not enough
-You can try to persuade someone not to do it, but sometimes it doesn't help.