Habits are driven primarily by the subconscious mind. You cant undo bad habits overnight what you have done to your subconscious mind over the years.
The subconscious mind will accept any thoughts that you keep repeating to it. We see this in action when messages are internalized through television. This is why social agents such as educators, religious figures and celebrities are so important. Their concepts are so important that the people who listen to them can't help but be seduced by the ideals.
Its up to you in the beginning to layout your definite purpose, write it down so it is understood clearly, memorize it, then repeat it like a mantra until your subconscious mind picks it up and automatically acts upon it.
If you emotionalize any concept and repeat it in a state of enthusiasm and back it up in a spirit of faith you find that the subconscious mind will adopt it more quickly positively and defintely.
The state of faith is the best way to influence the subconscious mind to adopt any purpose or concept. This is why ideas can be a powerful tool for doing good or evil.