I think that is a minor problem, maybe even just a mental block. In recreational and medical states you can buy a pre-rolled joint and toss whatever you don't smoke. In other places you can just buy the smallest amount and then throw away or give away whatever you don't use so you won't be tempted. Get rid of your glass and make a little "pipe" out of an apple if you want to smoke without having leftover resin-glass to tempt you. Eat or throw away the apple when you're done.

I mean thats like saying you can't quit binging on alcohol because beer comes in a 6-pack and you only need one can to get buzzed. Or like saying you can't quit stuffing your face with pizza because you can't just buy 1 frozen slice at a time and your pizza cutter might have residual cheese on it the next day to tempt you.

I know how hard it is, because I've "quit" and relapsed several times now but you gotta face the fact that you'll never have success if you mentally sabotage yourself with excuses like that.