That's a good way of looking at it. Start doing things for yourself, build yourself up, and you'll become stronger (and maybe make some new friends and contacts) such that leaving doesn't feel like as big a deal as it does right now. In the meantime, you'll have built up a life and interests that will mean your life after divorce will be great - and much less scary to imagine.
When I realised I had to leave my DH, it gave me strength just to know in my own head that I was going to do it. It was my own secret for a while. I was able to make small plans, and celebrate small victories on the way, and to celebrate milestones (this time next year I'll be single...).
By biting this off in small chunks, they each feel more managable and therefore achievable, and also the milestones come along more often, which in itself helps to show you're making progress.
One of the first things I did was to see a solicitor. Just to see what I'd need to do when I'd finally decided to take the plunge, what information I'd need in order to start divorce proceedings, and roughly where I'd stand financially. I didn't then do anything with that information for a few months, but just knowing it felt like I was closer to doing it, plus it meant I could start to picture what the process would look like, which in turn dimished its scariness in my head. And when the day finally came that I could stand it no longer, I was prepared. I knew exactly what I needed to do.
You can do this. You deserve a happy life and it will come, just as soon as you're ready.