context dependency

Key to shaking or forming a habit is the context. Learning is, to a large degree, context dependent. When you remember the loaf of bread you were suppose to buy when you're back on the front steps of your home, it's because that's where you were told to buy it. Context-dependent learning is why it's easy to not utter profanity in a church but much harder to remain pious at a bar; we learned particular behaviours in particular settings and thus work well when the behaviour performed matches the setting.

To study well, do nothing but study at your desk. The minute you become tired, leave and refresh yourself, so that only positive feedback is associated to studying at your desk. The same principle can be applied to up the quality of other behaviours; only eat at the kitchen table to have healthier digestion; don't read, work or exercise on the bed to get a better sleep; allot a room solely for romantic uses and your partner will feel the difference :P

So conversely, the first step to shaking a habit is to take yourself out of the habit's context. You're not likely to become atheist living in a church, nor stay sober if you keep visiting the pub. Pretty intuitive. It's when leaving the context is impossible that it becomes hard... The work-around is to revamp the environment as much as possible, but it's still a matter of starting starting a new behaviour in place of the old habit.

Slow and steady does it.

Lynch R, Leo S, Sowning K. Context dependent learning: its value and impact for workplace education. Education and Training 2006; 48(1): 15-24.