Do they ever miss the life they had before ?

[user1470296287]

Just that really,

I wonder if he is stung by the memories/history of a life before separation and ever think what on earth was i thinking.

Lots of years together surely does it just disappear because someone else is in the picture.

I was with my ex wife for 15 years. I miss the daily contact with the children however, she occupies no head space of mine other than where the children are involved.
Don't look back OP, look forward

I think everyone misses some things. I still miss the happy times that ex-P and I had; there just weren't very many of them by the end of the relationship. It doesn't sting anymore, though. I'm living my new life. On the basis that nobody leaves a relationship they're happy in, I'd guess that your ex wasn't happy and so, while it's unlikely you never enter his head, he's probably moved on emotionally as well as physically. And so should you. Like Naze says - look forward. Look forward to making new memories and enjoying new experiences, don't let whatever your ex is getting up to hold you back from that.