All habits can be divided into 2 categories - harmful and useful. The former, unlike the latter, usually do not lead to anything good. Different habits are disposed of in many ways. But the general principles will be useful to all those in need.
Instruction manual
one
You can defeat a habit only by understanding its cause. Watch yourself from the side, find the "irritant" or other reason. If from a conversation with your mother-in-law you start to bite your lip or scratch intimate places - everything is clear. Try to less contact with the "irritant".
2
Note that a habit becomes one if it gives you some pleasure, increases the emotional background. Find what you like in your bad habit and reflect on how important the habit is to you. Maybe she does not bring the desired effect.
3
Make a firm decision. Find positive points in getting rid of a bad habit. But if this does not help, you can do otherwise. Lose in your brain what will happen if you break your promise to yourself. Or you can bet a substantial amount of money. Perhaps the fear of a disorder that may occur in the family, or the fear of losing a lot of money, will overcome the desire to continue smoking or drinking (for example).
4
Try to get a new habit. And make it so that the new replaces the old and brings the same pleasure. Suppose you have a habit that affects all the pens and pencils that fall into your hands. You like to nibble them. Replace this addiction by drawing small pictures on a piece of paper. A break during work can be changed to the use of coffee or tea.
5
Self-control is considered one of the most difficult approaches to a bad habit, but it is sometimes the only way to get rid of a habit that torments you. Consider a specific example: you often use parasitic words in speech, sitting behind a chair, dangling your feet, tugging at the edge of a blouse or sweatshirts. When preparing for a small talk, think through everything to the smallest detail, right down to how you sit in a chair. Before speaking in public, also learn your speech, so that without hesitating, which provokes the use of harmful words, everything is said.
Useful advice
And remember - there is no weak will, there is only insufficient motivation. Therefore, be patient, gather all your will into a fist and you will defeat any habit.