Haha, not ANY addictive substance. With a lot of them that "pink cloud" doesn't arrive for a hell of a lot longer. Take methadone for example, at day 4 you'd be wanting to kill yourself and the only reason you don't is that you're too sick and weak to even be able to do it. I do know what you mean though, there is always a period when people feel really proud of themselves for quitting and think they will never use again and it suddenly feels easy, but I'm just explaining that
when that occurs greatly varies from substance to substance, and person to person.
The thing about opiates is that the severity (and length) of withdrawal really depends on the person, how long you have been taking it, how much you've been taking, (and of course which opiate it is). Someone who has been using 0.1g heroin for 2 months is going to have an entirely different experience quitting than someone who's been using 3g for 20 years. My advice to anyone even considering quitting is
do it now, because it will only get worse.
Some of us are legitimately in a position where the hardest part IS the withdrawal (which in my opinion also includes all the mental/emotional effects).
ETA: Congrats to the OP by the way. Don't let anyone minimize your accomplishment, just don't get over-confident either. Remind yourself constantly about all the things you didn't like about using and how the withdrawal felt and why you never want to use again. Good luck