While I don't think it's good to beat yourself up, having some goals like this is really good. That's kind of what I'm doing too. I was never really one to exercise and that was fine when I was younger and my metabolism kept me on the light side, but reaching middle age it has become quite clear that this can't continue.
Now that I've been doing it a few months I'm kicking myself for not getting my arse up sooner. I probably would have felt a lot better in my 20's. Oh well, life is for learning.
Good luck on your journey.