I recommend reading "Shantaram" if you want to get a written sense (not that I can confirm its accuracy) of the total hell that is cold turkey off heroin. Both may be tough and painful to quit, but in "Shantaram" the turn off heroin is described as: imagine everything that is in any way good in your life, your being: warmth between your toes, energy to look up at the sky, hope for tomorrow, etc: now imagine every single shred of that positive-chemical-energy is shredded. What's left is all the horrible pain of being with none of the chemicals that help us get by. Or something like that. Great book, mostly about Bombay in the 80s and heroin only has small focus, but really worth the read!