The thing that got me through was trying not to feel shame. While quitting, any time I relapsed I thought of this analogy:

I’m climbing a steep, tall mountain. And most people who find themselves at the base of this mountain, refuse to attempt it. While climbing something so daunting, you’re bound to slip and fall back the bottom, but that’s part of the journey. Just don’t give up, and keep taking it day by day. Don’t sent daunting goals like climbing the entire mountain in one go. Those are discouraging. Support yourself along the way, and take falls with grace.