Outgrowing a friend doesn’t make either of you bad. Sometimes two people just grew in different directions.

There is no villain in most of these, which is exactly what makes them hard to describe. Two people spend three years changing in directions that happen to diverge, and nobody chose it, nobody broke a rule, nobody can be blamed for it afterwards. The pull toward making one of you the bad one comes from wanting a reason.

So practise saying the plain version, to yourself first and to other people if they ask. We grew in different directions. No story underneath it, no evidence for the prosecution, no need for anyone to have been wrong.