The Talmud says it very well. The second time a person sins, it appears to him as though it is permitted. The third time he sins, it becomes like a mitzvah. Here's the secret to using habits. You see, there is another aspect to habits that we didn't mention yet.
Habits remove the thought process from the action.
It makes you do things without thinking. This is the way it is done, so I will continue to do it this way, even if it may not be logical or make sense. That is the key to growing and accomplishing as person. Don't stop to analyze whether or not you should keep Shabbos or give charity. Make the good deeds in your life into habits.