I could only truly stop playing it when I completely internalized the fact that the game didn't bring me anything except misery after every match, win or lose, and the short term satisfaction of the ding you hear when you kill a creep or make a fancy play were not worth it.
Sometimes when I remember it exists I still feel a pull towards it, but now I know that if I play it, in 45 minutes I'll wish I did something else instead. This is more than enough to stop me, fortunately.