As cliché as it may sound; "Only time can heal a broken heart."
Moving on means (letting go).
The biggest challenge most people have early on is accepting the fact that the relationship/marriage is over. Hoping for a reconciliation keeps one from moving on. You can't get to second base while holding one foot on first base. Commit to moving on.
Needing "closure" also makes it hard to move on. Anyone who puts their life on hold until they've gotten some explanation from their (ex) is giving them way too much power over their future!
There is nothing your ex can say or do that would make you feel better about having your heart broken!!!
Let go of the idea of trying to learn/discover something you need to change about yourself. The reason he/she broke up with you could very well be the same reason why the next person falls madly in love with you! Changing for exes is changing with every shift of the wind.
Romanticizing the past also keeps people from moving on. This is especially true if they're not dating or are having a challenge connecting with someone new at that moment. They'll only remember the "good times" regarding their past relationship and conveniently forget about all the arguments and disappointments.
The truth of the matter is; in order for (him/her) to be "the one" they would have 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!
Put things in perspective. When it comes to love and relationships most of us (fail our way) to success! If this weren't the case we'd all be married to our high school sweethearts! Welcome to the club. You didn't die! You're not alone!
An ex is an ex for a reason and it's usually a good reason.
Your future lies ahead of you and not behind you. Best wishes!