The only way to "move on" is to let go and (focus) on other things. Your future lies ahead of you and not behind you!
If your relationship ended accept that it's over and put away any reminders of it in storage. Unfriend your ex on all social media, delete phone and email contact information, and avoid going places you know your ex frequents.
Stop "romanticizing the past" by wearing "rose tinted glasses". Having "selective memory" keeps you from seeing things for what they are.
In order for your (ex) to have been "the one" he/she would have had to see (you) as being "the one".
At the very least a "soul-mate" is someone who actually WANTS to be with you! (And vice versa).
Allow yourself time to grieve among your close friends.
Get back to doing things you love but may have neglected while you were in that relationship. Set some goals that have nothing to do with your relationship status.
Put energy into your career, learning new things, traveling, working out, and living well.
That (person) who you can't imagine living without just know this: There are over (7 Billion) of us who are doing exactly that every day! In fact (you) use to be one of us.
Eventually you'll meet someone new and fall in love.
You'll tell yourself if it hadn't been for my breakup with my ex I would have never met this "great person".
Every ending is a new beginning!