Welcome to the Forums. I'm sorry to hear about your situation, it sounds like you have a had a tough run over the last 4 years of your relationship, and perhaps neither of you were happy in that situation for quite a while.
First of all, it is natural to feel how you are feeling. Ending a long term relationship can seem like such a massive change over night, it is natural to be afraid of meeting new people and being alone after such a long time not having to worry about these things. The short answer to your question is that there is a light at the end of the tunnel, you will meet new people, develop new relationships and move forward, as long as you are open to letting new people into your life.
Your ex partner is likely dealing with issues of his own, but these do not reflect on you personally as being "not good enough" or "having something wrong with you". Its easy to blame ourselves when a relationship ends, its a simple answer as to why it ended, but in reality when it comes to relationships its so much more complicated than that. I wont begin to pretend I know the details of your 4 year relationship, but from what you have said it seems at least part of you is glad that you have gotten out of that situation. That doesn't mean it's easy, or that you shouldn't be upset, grieving over loss is a natural process by which we can acknowledge things in our lives as being important in our past, before we are able to put them behind us and move on.
It will be a gradual process, but as long as you know what you want, it will get a little bit easier each day. One day you may look back and wonder how exactly it was that you got from this point now, to where you will be in the future.
If you are really struggling with this break up, and feelings of self-worth, blame etc over the coming days, that is something we can talk about more, and I would be more than happy to help in any way I can. Either by helping you to understand these negative thought patterns, or on a few relatively easy ways to start dealing with them.
Hope this finds you happy and well, but if not, we are all here to help.