Don't ride as hard as possible every day. May sound obvious, may not, but your body does need some time to recover, especially early on.

I found that as I got more fit, the onset of the burn got pushed back further and further - in other words, I'm able now to ride longer/harder before the onset of the burn than I was years ago. I don't know if you've read much about this stuff, but here's a starting point re: lactate threshold (LT or "the burn"):

http://www.velonews.com/train/articles/8217.0.html

You might also want to follow the link in the story re: VO2 max.

Keep those legs moving. You'll be fine.