Developing a heroin addiction takes time and effort - it took me a decade of sporadic use then a year of fairly regular use to become a full on addict. That's not to say you can smash the arse out of it mind you - try to impose some limits; like don't use for more than 3 days back to back, then leave it a good week before having more. Also be constantly on the lookout for any physical/psychological symptoms such as lethargy, lack of motivation, cold/flu symptoms and cravings. IME, physical withdrawal symptoms were noticeable long before the psychological cravings kick in. But once the cravings hit - you're fucked as the physical & psychological withdrawals synergise to create a beast greater than the sum of its parts.
That's the catch though, that takes willpower (which I seem to horrendously lack). If I go buy H and use for the day, I find it very difficult not to use the next day if it's there - then I'm fucked anyway as I know the 'lethargy, lack of motivation, cold/flu symptoms' are going to happen now anyway, so I may as well keep going. Then after two weeks usually think '...what the fuck am I doing? I need to get a grip here', and let myself have a week of misery. Then I think, 'it wasn't too bad, maybe I can buy some more and try one of these chipping rules'... then I just stray off the path into the thorny shrubs, again. Ad infinitum.