The biggest reason people fail at creating and sticking to new habits is that they don’t keep doing it.
That seems obvious: if you don’t keep doing a habit, it won’t really become a habit. So what’s the solution to this obvious problem? Find a way to keep doing it.
When you look at it this way, the key to forming a habit is not how much you do of the habit each day (exercise for 30 minutes, write 1,000 words, etc.), but whether you do it at all. So the key is just getting started.