Why do people go through rehab? Are there different kinds of rehab?  
We have AA for alcoholics, as well as clinics and retreats...places one can be admitted to for programming or is it reprogramming? Changing the way the mind thinks so one doesn't crave a controlled or uncontrolled substance, legal or illegal substance.  Steps one must go through to over come a behavior that lead to the addiction in the first place so that one can relearn how to exist with out it.
Once this individual has gone through the process in its entirety...the now recovered addict, moves on.  That doesn't mean that person doesn't remember where he or she has been-how does one forget being addicted to something. The craving, the high, the feeling of the affect it had on the body, the mood change, altered state one enters and remains in until it-the substance- wears off.
Does the addict remember what it feels like to come down from that high..why sure. See just because you go through the program, through the therapy, through the withdrawal from it all...learn to exist with out it, move on per say and consider it just a part of your can retrain the body, rewire the mind to live without the substance, but yah never quite forget the memories of it. Sure they may fade as time goes by as one continues to practice sobriety...but I'm sure there are good days and bad days with that too.
    Hence the reason people fall off the wagon or start using again. It's those memories that get yah every time. Creepin around in the mind as if to prey on you looking for a moment in life to jump out at you and say "hey remember me?" And it all floods the body like a rush - a surge of instant need for gratification, urge to quench the thirst, feed the hunger, to quiet the shake, to settle the voices in your head, to make the memories go away.
I entered rehab years ago. I stayed there till this very day.  But a very different rehab.  My addiction was out of control. I couldn't control much in  my life while in those moments...the craving, the feeling, the withdrawal, the feeling of withdrawal, I lost my body, I was losing my mind too.  To the point of why I think I have damage today...after years of living for the next high, the next escape from all the bad, the lows, the mindless ravaging cravings...years of thinking that way, behaving like that, for the next fix...getting it at all costs..remaining there till I no longer could. It's bound to take a toll. I don't think anyone is ever quite the same after addiction. Recovered or not. It changes a part of you that no therapy in my mind can quite reach, other than to hopefully give you skills by which to cope with. Oh did we abuse eachother.
I know I've changed.  I still crave, not nearly like I did. I remember the uforic feeling of that high. But I also remember the painful crash and burn. Coming down from that kind of high was insanity. It was more than the sweats or was the racing minds, uncontrolled thoughts, the emotions, the craving, the craving, the lay on the floor screamjng and crying craving for more. Never knowing  when the supply would return.
Thousands of dollars later in therapy, cognitive behavior skills, all the rewire, all the modified thinking, one bad all jumps out and says hey remember how I made you feel goood....while i havent fall in off the wagon, tho I'm taunted  daily by those memories, tortured as I recall that feeling. I've gotten as close to using as it gets for me. I've sat in the presence of that satan himself. Filled with hate for me. 
I see today, where that addiction has lead me.  A journey I never would have thought I would take. A  chapter I'd never write. An experience I'd never take.  A substance I never thought I'd get addicted addicted..that it would try to take my life not once, but twice.  Too much of a good thing can kill you for sure.  Lesson learned. Lesson learned.

The substance, well, inanimate object as it is...has no feeling, compassion, respect, or anything period for what it does to you, no regard for the affect, side affect, just wants to get in your head and your body and make you feel oh so good..nevermind the consequences. 
It doesn't care how it fucks your life over. It feels nothing.  Has no love, no concern for you or your's just there to be convince you it's okay for you to use you and it, all while getting lost for a little while. Four or five hours of esextacy whenever it gets an opportunity...or perhaps the one hour or so quicky cuz it can. Just to get the high. And make you crave it more by messing with your head.  Have you ever been so high you imagined your substance actually really loving you? Talk to it as if its real? Pour your heart out to it after just getting high as if it cared? Day after day, yeeearvafter year. Have you ever hoped and wished with everything in you, it could be real, because you never wanted that feeling to ever go away? Yeah that was me for years, talking to a figment of my imagination.a substance I couldn't control, I substance I wanted to use every second of my day for the rest of my life.  Cold harsh reality.  Wasn't possible. I wasn't a good enough host for that. That addiction ruined me, changed me for sure.

Rehab continues. 
Be addicted to another person, how that person makes you feel, the quality that person brings to your life and the life of others, and in my personal life, the love I found that in the end was not reciprocal- is an addiction so profound, that when cut off..brings a grief much like that of the death of a loved one.  
If this is you, and you are anything like me...find the community or professional help you need to deal with your loss. It is real, it is painful. You are not crazy. You are grieving the loss of someone who you loved...that is still living and all to often living another life- without you. 
A phenomenon that will so mess with your head that you will believe every negative thing that x said about will change your outlook, your behavior, your perspective, perception, everything about how you see yourself and your world.  
Its not a bad thing to need help.  Its not the end of the world if you have a bad day, just don't stay stuck there.  (Practice what I preech). 
Stay strong.  Addiction is not worth dying for.  He is not worth dying for.