It's totally possible to taper yourself down - but it does take a lot of will power. First you just have to limit yourself to one session per day, at night time. This way you'll get all your other shit done first.
Then, once you're solidly on a once-daily routine, start packing smaller and smaller bowls - just a little bit less every day. This is actually probably harder than limiting yourself to only one smoke a day, because once you're high it's a lot easier to just say "ah fuck it" and pack some more. I just make sure to put my weed away and put it in an inconvenient place so getting up to pack more will be a pain in the ass. Plus, I try to think, "well, am I pretty high right now?" and I always am... so there's really no need to smoke more weed. Over time you'll notice weed hitting you a little harder and eventually you'll get down to one or two hits a day - pretty fucking reasonable if you only do it a couple hours before bed.
Another good trick I've picked up, which may help you, is to always leave a little bit left in the bowl - that way you smoke less and the next day you've already got a little bit packed already, which in turn means you put less fresh weed in. It's a win/win!