Sounds to me that what you may feel as the "worst" thing (being 17 yrs old), is in fact, a good thing....Unless I'm misunderstanding you.

Isn't it better that you've stopped this behavior at your young age now, as opposed to your later years? With that, it cannot be a "bad" thing, therefore not a "worst" thing?

Be proud of yourself that you are trying to redirect your life.
I can't help to be concerned, though, that by quitting all those habits simultaneously maybe you are possibly setting your expectations of self a bit TOO high to begin with? (In other words, sabotage yourself of success by putting too much strain on yourself by quitting all of those at once?). That is a lot to quit at once.

I must admit, you have great strength for accomplishing this for the duration you have already.
Be proud of yourself. You have every reason to be.

Shangrala