Why can't I just block him out and move on?

It's a long story but I can shorten it. Basically my ex led me on and really hurt me badly. He has a new girl now, just two days after we ended things for good.

I deleted all of our texts so I wouldn't be tempted to read through them and I unfollowed him on Facebook so his posts wouldn't show up on my newsfeed, I unfollowed his friend and girl too. My friend says to just delete them and I'll feel better but I'm too scared for some reason! I can't bring myself to delete his number either.

We haven't talked ever since the day things ended. It ended with a four text conversation and he said if I need a friend or need anything at all he will be there for me, which I don't know how much I believe: I still care about him a lot and part of me keeps secretly wishing he'll message me but the other part of me hates him.
Why can't I just block him out and move on?
Post Opinion