Every relationship is a learning experience. When a relationship ends you should take time to figure out what went wrong and reflect back to what your contribution to the demise of the relationship was.
What could you have done differently? What lessons did you learn or will you take into the next relationship?
For me I think I should have spoken up more. If something was bothering me I held it in and never said a word out of frustration. In the end my partner ended up taking advantage of me.
I no longer do that and I can tell that it has made a difference.