i think keeping busy is huge.
i've made tons of new friends the past few months and try to have something planned every night of the week. even if i am stuck at home alone, i try to keep my mind busy by reading or doing a puzzle or watching a movie i've never seen.
i promise, promise, promise you that it gets so much easier. it will take time (god, i used to hate when people would tell me that!) but i would swear my life on the fact that you will gradually think about him less and less.