Going back to a friend you dropped takes a sentence like “I wasn’t a good friend to you.” Say it whole.

Walking back toward somebody you let go of requires naming what you did, without softening it into a misunderstanding. Half-apologies are the usual attempt: you got busy, things got weird, life happened. Those protect you and leave them holding the question of whether it was their fault. The full sentence costs more and is the only version that clears the ground.

If there is a person you drifted from on purpose, send one message with no excuse in it. Say what you did, say you are sorry for it, and ask nothing. They may not come back, and you will have given them something true either way.