If you want to do it, you should do it. You'll learn a lot from it, and just because you do it doesn't mean you have to publish it or even show anyone (although, you'll learn more if you do show it to other people). It's a book, not a life-time affair. When you're done, you will write a different book. And then another. The important thing is that you want to do it, and you follow through and write it instead of wiffle-waffling.

(Don't do it for praise and international acclaim, though (-:. I mean, it'd be nice if those things came, but I think it'd be a fluke. Do it for personal growth as a writer.)