I think learning to live in the moment is one of the biggest things about the post-quit learning to live business. That's where I find myself struggling, too. Both learning to accept the moment as it is (that is, not changing it with substances) and also letting go of shame over the past and fear about the future.
When it comes to the past, though, I just try to keep in mind that the more I improve my life, the more those past embarrassments will fade away. I'm pretty sure that at some point one of my current friends will say to someone newer, "You know, Fantail used to be a huge party girl!" and new person will go, "Weird!!"