A friend once asked me - how do I make a habit out of good things? I then wondered - why is it so hard to keep up an orderly routine? Two great Qs... down below, the only two answers you need:
1. We do what's easy - the less effort, the better. Thus, an action will become habitual if it is effortless. How many times haven't you opted for the easy way, even though you knew dead well it wasn't the best way? :)
2. We seek great rewards - so naturally, we make a habit of those actions that carry a very large reward. This reward can be physical (we see it w/ food) but also intellectual, to do w/ our psyche. It can also be numinous (take the case of diamonds, for instance - we want them and we buy them cause they fulfil a great need for mystical energy at an unconscious level).
You might get this twofold explanation easier w/ the help of a personal example:
I go swimming everyday. It's become a habit. But why?
Is it because it's easy? No - since I must pay for a membership, get up earlier to account for time spent swimming, make sure I dry my speedo after the sesh, and so on.
Is it because it carries a large reward? Yes - I get to enjoy the hot, warming time in the sauna post swim (physical reward), I see plenty of hot, attractive men (pleasure reward), and I feel and look great (yet another physical reward).
What habits will you introduce in your daily life - now that you know how habits are formed?
P.S. to explore more about habits and human behaviour, try reading Supernormal Stimuli by Deirdre Barrett, or
Human Behavior and the Principle of Least Effort by George Zipf .