Using pain and pleasure to form habits

Achieving something regularly, especially when it comes to building a new habit, involves motivation. Motivating yourself daily can be hard – life gets in the way, things stop being quite as interesting, you lose the initial zeal, and so on… But there are ways to ensure that you stick to the habit, which is where the principle of carrots and sticks come in.
Carrots are rewards/pleasure.
Sticks are penalties/pain.
Your motivation can be boosted by adding rewards and penalties (especially the latter, as the fear of losing something is a greater motivator than the pleasure of gaining something).
For instance, if you want to create a daily workout habit, the reward can be having a (reasonable) portion of your favourite ice cream at the end of the week, if you stick to your workout plan for the whole week. But that alone might not be enough to make you stick to the habit. So to make it even more effective, you then add on penalties, like: paying £1-10 (or more) for any day you miss your workout. Make the amount something that will actually make you feel the pinch.
The combination of pain and pleasure, I’ve found, is the most effective way to create and stick to regular/daily goals, namely goals like building a daily habit.
You need both carrots (pleasure) and sticks (pain).
What habit do you really want to form?
What rewards and penalties will motivate you to stick to them on a daily basis?