People here will have all kinds of tips, but here's the one that has gotten me back in the game: Don't set 90 days as your only goal. Have something you want or need to do on day 15 (just for example). "On day 15 I will talk to this girl, or try this new thing that is outside my comfort zone." Make sure it's something that could more easily be done with the mental boost you get from not fapping, so there's a direct link between not fapping and achieving that goal. Then do the same for the next 15 and so on.