The problem is the personality type using the substance or drug. Take the following examples,

The lonely guy who visits escorts to combat that loneliness.
The guy who loves being high and buzzed using stimulants.
The guy who has a short fuse drinking too much.
The guy who is naturally skinny using drugs to keep him bigger.

These are only a few examples and all will end in disaster for the person because when they stop doing the issue returns and off they go again.

The ONLY way and its difficult ,to stop using or doing anything like this , is to disassociate yourself from everything that is involved in it and this is the problem as it leads to a sort of emptiness. Best thing is to have goals in your life and do them. If you like music play something, if you like to run, run. Have balance and purpose in your life. Its easier said than done especially these days. I have buddies on coke. I call to them now and then and its the same old shit and its being like this for a long time. All the things they wanted or were going to do havnt happened.

Some people though are quite happy even if they are killing themselves.