It's hard to shake off a psychological dependence on pot because it's almost like your whole emotional currency is invested in it. Eating, sleeping, listening to music, reading, just being interested in anything - when you smoke pot regularly it's easy to feel like none of these things would be as good without it.
I quit being a daily pot smoker some years ago and what got me through it was the same thing that got me through giving up cigarettes 20 years ago - focusing on the novelty aspect. When you concentrate on the fact that you've made a major life change and that your existence is going to be different from now on, it's a huge motivator. You have to keep your brain interested. As soon as the novelty of not doing it wears off, that's when you're tempted to think screw it, what's the big deal anyway. You're selling your mind the concept that life is better without the drug, and you'll lose that sale unless you keep on top of your marketing campaign.
Maybe twice a year I will acquire a little pot for one reason or another and I'll go through this same thing in miniature. Just having a wee toke every night for a week is enough to start bringing that psychological dependence back - when the pot's almost gone there is that depressing feeling that the good times are almost over, that it's back to the potless grind, and wondering how I managed to be happy without it. Even after a week. Yet when it's gone, it's amazing how quickly your mind just adapts to the "other" state of not needing it to be happy. Which after all, is your natural state.
Cutting down is a lot less drastic than giving up entirely however. Back when I was a daily smoker (wake 'n' bake) I decided to cut down and started denying myself a smoke until after 6pm. I found this quite easy to do, appreciated how much better my mind worked during the day and enjoyed my evening toke way more than when I would smoke all day. You need that contrast to really enjoy stuff. Being stoned all the time, you're never really "stoned." Having the occasional toke is far more enjoyable - you appreciate it more and it has a much stronger effect.
I find that learning to sleep without it is probably the hardest part. You have to take steps to relax at night - avoiding bright screens is important (install f.lux), replace any "full spectrum" light bulbs with soft yellow light, drink some kind of sleep inducing tea (lavender, chamomile etc) and take a melatonin pill.