I haven't relapsed once since my last drink.
Really, I'm not sure I've ever relapsed, in the sense of drinking again after a long period of sobriety where I planned to never drink again. I've failed to quit, or quit for short periods and went back, but those aren't really relapses in that sense. I went through a lot to get to the point of really quitting, but it's been a solid 6+ years since then, and I've never really come close to relapsing.
I think the main reason is, I've kept sobriety at top priority above all other things. And I kept involved with support groups and made sober fellowship part of my new post-drinking life. There are lots of tools involved, thing you learn to help yourself - planning ahead, for example, what you do and don't do in different situations, but I think those would not have worked by themselves, for me. I personally needed the attitude that nothing matters more than sobriety, and the sober support from other folks in similar situations.