I was in the same boat when destiny first came out. Then I maxed out my characters and got most of the exotics and stopped. Then VOG came out and I started up again and then stopped when I got all the new content. Same with the CE and HoW DLCs. If you play this way, you'll find it easier to limit yourself. It may be different from you because I'm more of a completionist when it comes to gaming. Another suggestion would be to only have one character. You might be less inclined to play if you only have one character. Other than that, maybe have one of your friends create a password for your console so they can force you to pace yourself. ...or you can just delete destiny and save your progress on a flash drive so you have it in case you ever want to play again. I don't think is the way to go since destiny 2 will eventually come out and then you'll have to force yourself not to play it (good luck with that)