When I experienced this, I got to the roots of my issues and worked from that. My emotional numbness was the reason for these coping mechanisms.
I also set myself a 5 year plan - to be living independently, financially and mentally stable. With this, I had to realize that my habits of drinking and smoking will not effectively contribute to the achievement of this goal.
I was also smoking and drinking a lot because I was too depressed to realize how great I am (not bragging lol) but seriously, try and realize your own greatness by identifying your uniqueness and set of capabilities, even if no one else is able to see it.
The easiest way I've found that you can stop them is by replacing them with healthier ones instead. Coping is not a bad thing it itself, but it's best to use the means that work short-term and long-term instead of short-term ones that are going to cause harm in the long run. After all, that will only give you more to cope with later on. Ask yourself what are some healthier alternatives to drinking and smoking? When you get an urge to cope in an unhealthy way, you can try doing some light exercise, listening to some music you like, connect to some good people you feel safe to talk to, practice one of your hobbies or do something physically relaxing such as a nice long shower or bath. The more you practice healthy coping mechanisms the easier it gets to practice them again.
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