Unfortunately, there's no such thing as a shortcut to change. Simply by Googling the phrase “how long it takes to form a habit”, I found that the often cited time frame of “21 days” is a considerable underestimation that dates from the 1960s.
A more recent and relevant study published in the European Journal of Social Psychology suggests that when we want to develop a simple habit like eating a piece of fruit each day or taking a 15 minute walk, it could take us well over two months of daily repetition before a behavior becomes a habit.
Although 66 days proved to be the average length of time required to make a lasting change, there was a wide variation in how long habits took to form across the study. As you might expect, drinking a daily glass of water became automatic very quickly but doing 50 sit-ups before breakfast required more dedication.
The research also suggests that while skipping a day here or there isn't detrimental to overall success, consistently practicing the new habit in the first several weeks helped people shift from the act of “conscious self-control” to successfully “just doing it without thinking.”
Just like everything in life, practice makes perfect -- or in this case, a healthy habit.