It doesn't compare to using marijuana or being drunk, it's a totally different experience. You're mostly oblivious to your surroundings, relaxed and pain free. You also only have a handful of hours before you'll be sicker than you can imagine.
Withdrawl from opiates is unbearable. You ache from inside of your bones, always from your legs, and if you're in really bad shape from your forearms too. From the outside one may think that two or three days of aching isn't too bad. The biggest problem is that time passes more slowly than you can imagine, and you won't sleep. It's 72 hours without sleep, aching from deep in your bones, a throbbing pain in between your calf and you tibia that just won't quit. Your legs are constantly moving, because movement give you the sense that the aching is ending. You can't eat, you can't focus, you sweat uncontrollably and you teeter on the edge of sleep, but you don't cross that threshold.
The absolute worse thing is that you know that with one little bag, for just a few bucks, you can make the pain stop. You do't have to wait 72 hours, you can make the pain stop instantly. You think to yourself, I'll use just one more to stop this agony, and then I'll quit for good. You can't quit though, not that simply, because the next time you're in all that pain, you think the same thought... "just one more." Its a seemingly endless cycle of misery.
Heroin addiction is all consuming, it takes over your entire life and eventually takes your life.
I've used heroin, it started with seemingly harmless prescription drugs and it evolved. It took over my entire life and I used for years, never thinking that I could stop. It's now been 10 years since I've used any drugs. I'm more proud of that than any of my PRs.