Yeah, exercise is important for sure. Actually just in general, your life feels a lot better when you're physically fit. But yeah isn't it crazy how horrible opiate addiction feels? I was on them for 10 years, I only did heroin for a while, it was kratom for years (taking a fucking lot of it many times a day, I'd wake up at 6am every day with my legs unable to stay still and my nose running and feeling the despair), and then I was on poppy tea for years. I liked poppy tea more than heroin (I never IVd though), and honestly the withdrawal wasn't worse with it, I felt sicker and it lasted longer but I was less restless. With kratom I would get restless BODY syndrome, I would lay awake all night in bed, thrashing my legs and arms too uncontrollably, sometimes I'd punch my leg as hard as I could for like 10 seconds straight until it went numb and I got 30 seconds of relief. At some point I would just start screaming, the feeling was so overwhelmingly maddening, and usually by day 5 I'd break down from lack of sleep. I'm prone to restless legs anyway, as a kid I had them a lot, especially at night, and I HATE HATE HATE that feeling. With kratom it spread into my arms equally badly, I've never experienced that except with heavy kratom withdrawal. With poppy tea it was just a need to squirm, not nearly as restless.
But yeah, I experienced a lot of those, but for 2 weeks I was visiting my family and my oldest and closest friend was also there. I was of course on poppy tea, and he was really on heroin, and I decided to try it. Every couple of days we'd drive into the city and score some. I didn't have any poppy tea with me so I was just doing heroin (nasally). I started to feel those withdrawals, and there is something uniquely terrible about them. There's this darkness there, this apathy, that was really bad to me.
Anyway yeah, I had resigned myself to being on them life, I tried so hard for so long, I did manage to quit for 8 months once and I still went back. I wanted to die I was so miserable, and I basically hated myself because, like you said, it's always tomorrow that you'll quit. I betrayed myself every day, it started to fuck with my head a lot. Plus I was in an abusive relationship which was ultimately the reason my addiction had gotten so bad, because I was trying to hide from it. I was fantasizing about how to die because it was a strange sort of mini-relief from the despair... ahh, that would be so nice to stop existing.
Then the relationship ended, and I started to come out of my cloud, spend time with friends, life my own life and not be an an emotional slave experiencing stockholm syndrome anymore. I was still addicted, and still having a lot of trouble with it, but I decided I needed to just make it happen for myself, because I felt excited about the future, but I knew opiates would prevent it from manifesting good things. I started to think about ibogaine, and over 2 months it turned from a passing thought to a fully researched and planned idea, into reality. I did a flood dose at home with supervision, and it changed everything for me. It interrupted my negative patterns basically, on some deep, semi-conscious way. It sounds like you've experienced a trip that has interrupted negative patterns for you too.

I experienced some light residual withdrawal symptoms after the dust settled, and it was hard to sleep for months because I'd get a bit restless but only at night, but I honestly didn't care, it was like, dude, you were insane for 10 years of your life, you'd have to be an idiot to go there. I haven't had a craving since, it's been 3.5 years. I also started exercising and making sure I was eating well, and I identified things in my life that weren't working for me and things that I wanted or needed (not material things but activities, people, stuff like that), and made some changes. I basically altered my lifestyle in the ways I felt I should. It sucks that you can't help that you have chronic pain.

But always just remember the fact that the most abject misery you've ever experienced is the result of opiates, and that should be enough to remind yourself that it's not fucking worth it.
Anyway... I finally made the investment and ordered a nice stash of both AL-LAD and ETH-LAD. I'm pumped! I've done AL-LAD in doses from 150-300ug a good handful of times and I love it, but I've only done ETH-LAD once and found it very interesting and nice.