This is so on point. I identified with everything you said here.I'm not really of the belief that each time you don't give in, you strengthen. I mean, let's face it. Brain chemistry is changed through prolonged exposure to heroin and simply does not ever return completely to its original state.
I use heroin occasionally after being addicted to oxycodone, dilaudid, and fentanyl for years. I use once to twice a week at max, and I have my own set of principles that I follow. For example, I never use two days in a row. I wouldn't really call this a "successful" regiment as the day after use I'm always dealing with strong mental cravings to use again. Living with these cravings is not "successful" in any way. Sure, I don't give into them, so you could say I've succeeded in staying away from being physically addicted for some time now. However, like I said I'm always dealing with either mental cravings or very minor physical withdrawals (mostly mental; my mind tries to trick me into thinking I'm in withdrawal so I'll redose) and patting myself on the back for not stumbling into the pit I'm dangerously dancing around.
If I didn't have serious pain issues I wouldn't use. The physical pain is way beyond a simple justification to feed my addiction. I wake up some days with business meetings planned or work-related activities that I have specifically not wanted to get high before... however, I'm in excruciating pain and grudgingly go out and cop some heroin in order to be able to perform at an optimum physical level while sacrificing some mental clarity. It's absolutely terrible, and I'm definitely on track to return to my pain management doctor after much dragging of my feet.
My advice to you would be simply not to use. If you're thinking about picking up again for the sole fact to "feed the monkey on your back," like Ho Chi Minh said your chances are VERY LOW of being successful. That monkey will strengthen at that point, regardless of whether your brain is actually continuing to recover in sobriety. My only point in regards to that is at some point the physical recovery of your mind ceases, you are sober, and left with a once addicted brain and your ability to make choices. It's at this stage that you either decide to live a different life or sadly, more commonly regress to your former addicted condition. Good luck... don't touch the dope.
To the OP - worry about the rest or your life "one day at a time," as they say. In 5 years, if you've maintained your sobriety, you can always make that choice to pickup a bag of dope. For now, why not give yourself a BREAK, give yourself a CHANCE. Thinking long-term like that always led me to using harder and faster than before, it creates this mentality of "one last hoorah" that just results in perpetual heavy bingeing.
Good luck man - find what centers you, and stay in the center of it.