Get some paper and a pen. Put it by the substance you are thinking of quitting. Even if you are not ready to quit yet, do this one, little thing. Before you use the substance, mark on your paper the time and the date. Write a line or two about why you’re choosing to use the substance at this time. That’s all.
If you do this exercise, there may be some times that you realize you have no reason to use the substance. You’re just doing it out of habit, sheer mindless, automatic routine. OK, write that down. You might choose not to use the substance after all, since you don’t have a good reason. The spell is broken by the paper and pen. That’s why I had you put the paper and pen by the substance, so it can be there, ready when you are not thinking about what you are doing.
There may be other times when you have a reason to use the substance. Write that down, also. As you do that a few times, you may see a pattern emerge. You will identify your cues. It might be a time, a day of the week, a feeling, a circumstance, a person, or some other thing that triggers the thought of using. These are your reasons for using. They are problems you’re attempting to solve by using the substance.