I'd say it depends on the individual and where they are in their life when they begin using Heroin. Some people just come across it try it and leave it. Some people, fall in love with it, lose site of anything else and devote their life to the waiting game lol. I swear when your not on H and you have a habit, your just waiting to do more lol.
I snorted H for 9 months, then shot up for about 4 months. When i was snorting it i eventually developed a tolerance and stopped for about 4 or 5 days and expierenced the withdrawals.. i wasn't too bad into it tho, it was like having a REALLY shitty flu for 3 days... in some ways tho i enjoyed the expierence... it felt like a spiritual cleansing of sorts... starting fresh.... when i was shooting i never shot enough to gain a tolerance so i didn't have to get withdrawals from that.
Later I was charged with possession of a controlled substance narcotic and used periodically through out my probation. Later on I got paranoid that i would get caught again and just quit it all together.
For me quitting wasn't hard. I never really got heavily addicted to it so there wasn't a great deal of fear as to facing life without it. I wasn't using it to run away from anything so much as to enhance my mood and it helped with social anxiety ... well cured it... I can't say it was easy for the people i knew that did it tho... they were addicted and quite amazed at how easy it was for me to quit.
Most likely tho no matter who you are, if you decide to make Heroin your friend, it won't want you to leave anytime soon and neither will you. I'd say quitting smoking cigarettes is much harder though. I don't want to quit those, but even if i did, I imagine it will take some effort.
I think technically It's not so much that heroin is hard to quit using as it is more harder for a person to come up with a decent reason as to why they don't want to keep on using it...
It never made me feel how people in the movies look tho, it always gave me energy and made me feel more alive... rarely did make me just not want to move and sit around like a super stoner...