I'm ready to change. Best friend/roommate isn't.

Background: 20-something longtime stoner with stoner group of friends. Started talk of quitting and cutting back months ago, with minor successes (a sober day here, one there). My best friend that I live and pay rent with (dude is just a year older) is just as bad a stoner as me, if not worse. I tell him all the time lately that being such heavy stoners is not a recipe for success, and that we ought to stop. He halfheartedly agrees and has humored me in abstaining a few times, hitting the gym sober, etc.

Where we seriously differ is that he's content with this pseudo-cutback kind of lifestyle, you know not being stoned all day but still getting stoned at some point every day. I tell him that slightly toning it down is not enough to let us hit our potential, which leads him to cite our grades (~3.9 for both of us), our jobs (both employed in respectable positions), and our health (hitting the gym nearly every day). At this point I find myself incapable of arguing, and I usually say something like, "yeah, on paper we're doing just fine, but we both know we could be doing so much more." But he doesn't buy it. I know for a fact I'm not a wholesome, present, or interesting person when I'm hazy and passive from smoking, and neither is my friend, but all he seems to care about is the achievements that go on a resume.

I'm finding it nearly impossible to actually QUIT with this lifestyle still intact. Glass out, ashtrays on tables, seeing my friend smoke, whole house smelling like weed every night. This is a once-in-a-lifetime living arrangement at a steal and I can't afford to move out. What can I do, leaves? Just pure inner strength and strict abstinence?