@Tara I know this question wasn't targeted at me, but as a user of heroin and crack / cocaine I feel I could chime in with my opinion, if that's ok.
Now stimulants (in my case crack or powdered cocaine) seemed to be mainly a psychological addiction. I found that the addiction was all in my head, and if I was lucky enough to have a day when I wasn't thinking of that all too powerful stimulant, I could focus on other things and be happy without it. And the longer I could keep myself distracted from it, the easier it became to get my life back together. Then before too long, it's been months since my last use and I don't even think about it anymore.
Heroin, on the other hand, while I do think it is a psychological addiction to a degree, you also get those nasty physical withdrawals too. You feel weak without it, you have hot and cold sweats, you can't eat, you have stomach cramps, restless legs, everything. And then of course because of all the nasty physical symptoms, it makes you think about it again. You can't think of anything else, so it's a painfully physical addiction but also very psychological too.
And for that reason, I will always believe opioids are much much harder to come off than any stimulant. This is of course my own opinion and others may think differently due to different life experiences.
Just wanted to share my 2 cents.
Stay safe peeps.