I WOuldnt look at it as being a bad thing, dont focus on the why has it ended...it has its reasons. Just look at it as the next positive stage in your life. If you focus on a negative too much it begins to comsume you and so you eat and feel it and it affects your behaviour.
Some people come into your life for a reason, a season or a lifetime. He probably came to your life gave you something and probably took away from you too (not a bda thing - you may have helped him grow like he did you) and you have both fulfilled your reasons to be with one another.
The above ideas are great and I would really look into something that takes your focus away from him.
But having said all this when a relationship ends we lose a little part of ourself and so feelings of loss and/or grief are very normal. Give yourself some time to accept what has happened but limit that time and then set small goals and make sure that you work towards them. Tell yourself that you feel better (when your given "self time" is up) and take, make and carry out actions that will make you feel better.
How you feel affects your behaviour and your behaviour affects how you feel. tell that voice inside your head that this is a learning curve that you will get past it and it will only take as long as you allow it to just tell yourself it neednt be 1 month or 1 year it can be a couple of weeks.
Just make sure you give yourself a chance to rest and recover
Take care hun, its not a nice place to be but how long you stay there is up to you.
*hugs*
uzz