Maybe it's how we know it,
Maybe forgetting someone isn't that hard.
Maybe being over someone is easy, after all.
Being busy all day, busy enough that our thoughts don't have time to disturb us.
Claim that everything is fine, that you did't think of him today, that you are cured of him.
Lie to yourself, until you start believing it.
Repeat that you deserve better, until you mean it.
Crawl back to him until the humiliation eats you from the inside and then cut any contact by fear of doing it again, again and again.
If that should have worked, that would have worked.
Maybe this is how we forget somebody.
O.P