Stop thinking about the loved ones as the best choice is to know it will take time until get over it. You should know that no one is perfect and if you lost for another or died or had a cross road. So you should lift up your spirit and know you can occupy yourself with a lot of thinsg around to make your mind away from thinking about.
Dwell only on the good things. When you laughed with him. Know that each person in your life helps you grow in some way.
Left you? Then just take it easy, you'll get over it. Died from you? Then I suggest sorrow therapy
It won't be easy at first but really it will get easy over time.
I was in the same situation few months before and that's when I join this site, hit up with a few guys and started chatting lots with them and helping ppl on here. Its amazing, I got over him in just weeks
Trust me you never get over it. Its been 2 years now and I still mourn as if it was yesterday. I know I havent given you any advise because I myself seek help.