I've had four natural births, and transition is definitely the most challenging part, no doubt about it. I think what helped me most is
1. being in the water. LOVE the warm bath in labour.
2. doing ONE contraction at a time.
Don't let yourself think about how much further you might have to go, or anything like that. Get through THIS contraction and then think about the break that will come. And then breathe, and let it go.
3. letting the contraction do it's work as best I could without fighting it.
4. Remembering that when you get to the "I hate this, I can't do this, this is awful and terrible" stage, you're ALMOST DONE. Get someone to remind you of that when you hit that point.
All the best for a great birth, mama! You can do it!