Panda, it isn't your fault, but your relationship with your ex was probably undermined because he was talking too much to friends and family about the relationship. Then there was too much scrutiny and commentary going on and you weren't hearing about it so you couldn't respond or compensate for it.
Anyway, you know that you need to move on, so here are some ideas:
1. Throw yourself into your work for a while. You said that you work a lot anyway, so just give it some extra effort for a while.
2. Adopt a low-maintenance pet like a cat, to get some unconditional affection.
3. Re-connect with your friends and family. If you don't have time to meet up or talk on the phone, at least send some emails or post on Facebook.
4. Start a new hobby, especially one where you might meet some new people.
5. Exercise. Or if you are already exercising regularly, change it up. For example, if you were doing yoga before, switch to free weights.
6. Do some volunteer work. You will meet new people and feel great about yourself.
Good decisions come from experience. Experience comes from bad decisions.