Let's say the "normal scale" for doing life as it relates to "pleasure" is a scale with units of measurement from 0 to 100 units, in which a "0" = task of cleaning a dirty toilet, and "100" = event of receiving a new car of your choice with no cost to you. When one has genetics for addiction and uses drugs/alcohol, the "high" from "weed" would typically be about a "300" which would drastically distort and recalibrate your "pleasure scale" as it relates to every day life. Should you use "meth", the "high" from that would typically be about an "1100". All of a sudden the best of "normal scale" of life = "100" (getting a new car of your choice for free), is now "boring". Getting "high" and living a life of being "high" now dominates your thinking, especially when under the normal stresses of life, and thus one uses again.
This is just one of the four factors of chemical addiction, the others being 1) "obsession" to use, 2) genetic piece which creates "craving", and 3) "isolation" in using which reinforces continued using . . . BUT after sustained abstinence and recovery, "Euphoric Recall" in my opinion is the predominant factor for relapse after long periods of sobriety.
Please feel free to leave comments! Look forward to your feedback! Best wishes in recovery!