I've been reading a fascinating book on the subject titled "The Brain That Changes Itself" by Norman Doidge. In it, two points are repeatedly stressed. The first is the following:
Neurons that fire together, wire together. Neurons that fire apart, wire apart.That is, neurons are the centerpiece of a lot of the activity within our brain. Whenever we act, several different neural pathways all fire simultaneously and invoke certain reactions in your brain. So for example, when you think of Chipotle, it might also trigger thoughts of their delicious burritos, their free student drinks, their distinctive brown paper bags, or images of your local Chipotle brand, or the general positive feelings you have towards the brand. And each time you think about it, these neurons are firing and you are reinforcing these images and connections in your brain.
My tip today is to become more aware of the actions you perform, and what other feelings or thoughts you associate with them. Think of ways you can improve, and learn to associate that with a relevant activity. As an example, I have been making it a point to stress both speed and penmanship while taking my notes in class. Every time I emphasize this, I am reinforcing both qualities in my general writing and noticeable improvement has already taken place.
Use positive reinforcement for those admirable things you do. Do the opposite for those bad habits you've been always wanting to kick. It's a process, but in time your brain will re-wire and you can change yourself for the better.
Disclosure: The author owns a position in Chipotle Mexican Grill.