A bunch of my friends are on this "21 day" thing. It's based on some study about it takes 21 days to form or break a habit. Some of them are trying to break a habit, like biting their nails. Others are trying to form good habits, like exercise or eating healthier. So every 21 days they add a new goal. Or, if they failed the last one, they try again.
I haven't exactly jumped on board, although I have adapted my no-sugar diet into their 21 day thing by allowing myself something with sugar once every 21 days.
My opinion is, it's all about managing yourself. Some people might do better making many drastic changes all at once, and some people might do best making small changes one at a time. And some of us are conflicted, and sometimes make small changes and sometimes huge changes!
Good luck with your goals! They sound like a great start!
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike