Gunslinger, the best explanation I have heard(in simple terms) as to why relapse is a normal phenomenon of recovery is this: Addiction is a bottom up brain disease, while recovery is a top down "treatment". Our brains are wired for survival through the reward system. When we do things like eat or have sex, feel good neurotransmitters like dopamine are released. This is what motivates and incentivizes us to do things. This reward system(mesolimbic pathway) runs throughout the brain, upper, middle, and lower.
This system works great until a substance like opioids is introduced. Opioids, and similar substances(addictive drugs) work on this same "survival mechanism" known as the reward system(mesolimbic pathway). So to the lower, sub-conscious parts of the brain perceive these drugs as "good for survival" essentially. All the lower brain knows is stimulation, and the drug produces much high levels of stimulation than normal, which is why people can crave drugs more than food despite being in starvation, or why a person can recognize the damage and destruction yet not change behavior. It is also why even after periods of sobriety, after recognizing the destruction, after learning a better way to live, after all that- you still might have an urge.
This is where time comes into play- you have to un-train your brain, teach it that it doesn't need those drugs to survive and feel good. It's a step that really can't be rushed and requires a lot of patience. Probably one of the more frustrating aspects as well.. things would be so much easier if I didn't have an urge to use still.
As for NA... I personally find many to be a bit negative and self-deprecating. Constantly introducing yourself and referring to yourself as an addict is directly contradictive with basic psychological principles. A person wouldn't identify themselves as cancer even though it is a disease they may have to live with. People don't identify as depression or anxiety- they say they have depression or anxiety. It is the same for addiction. We aren't addicts, we are people with the disease of addiction. I think it's done in attempts to confront denial and true acceptance of the situation... idk.. I don't want to be too negative because I like meetings but most of what I like is the social aspect not really their philosophies.