@Shigs69Like any grief, it's the times you're alone and it's quiet that the feel the worst. It's natural to want to know what you did wrong. But if there was something, I would thing you would have been told. If you find yourself having to ask yourself that question, then chances are the answer is probably nothing. If someone did something wrong to you and it was bad enough for you to break up with them... would you tell them what they did wrong as part of the reason for your decision?
As @Ru-bee said, a break up is like grieving a life you have just lost, and grief hits hard and then gets better over time. When you're ready you can then go about building a new life and finding that happiness again, this time with someone who appreciates you more. Or at the very least, tells you if you're doing something wrong before it gets to this point.
