Breaking a Vow?

I was baptized at age 14 or so, and as was customary, was required to repeat a baptisimal vow, a copy of which I was given after the service.

I've just found a link to those vows on the net, and in re-reading them I realize there are a couple of things that I actually don't agree to now, that I probably did agree to then.

Does this constitute breaking a vow? A vow made as a 14-year-old who may not have known better, or whose path has headed in an unexpected direction since?

When do vows become "obsolete"? DO they ever? If not, I'm in trouble! :)