The more time you spend wondering how best to approach something, the less time you have to actually learn the best way for you. You have to learn through failure, so you might as well fail faster.
Photo by Frinthy
Developing habits to help you reach your goals is a lot like developing software: you won't know what doesn't work until you test it out. Leo Babauta at Zen Habits recommends you worry about fixing the bugs after you ship your new habit out:
Get it going as easily as possible, so you can gain real-world info. Do the habit for just 3 days -- this is an iteration of your habit method. Don't aim for 30 days, just 3. After doing the habit for 3 days, do a 2-minute review: how did the plan go? Did you do the habit every day? What worked? What got in the way?
Now you have data you can use to fix what needs fixing. Stop wondering what the best way to go about it is and learn what it is. If your workout was too hard, tone it down a little. If you can't remember to save some money on your own, automate it. It's better to learn what needs fixing than to not know anything at all. Ship out your product, find out what's wrong, and patch it. Eventually those habits will be bulletproof.
Fail Faster at Habits [Zen Habits]