Living with an heroin addict

I found the quote (left) and the words are exactly what I think addiction is. 
My ex-partner is an heroin addict and he lives in his own addiction community with his addict friends - or should I say, runners? Addicts don't have friends; the people they associate with are leeches that feed off one another. 
My advice to the person who posted:
He chose heroin over us  is not to take it personally. But not taking it personally is hard when you have a young child who has been abandoned for a tenner bag of smack. 
I have lived with an heroin addict and living with an heroin addict is stressful. They lie better than Pinocchio; can act far better than Brad Pitt and tell stories JK Rowling would be jealous of. An heroin addict does not live in the real world. Their world consists of chasing the high and they aint gonna get it! 
There is only 1 high and an heroin addict is constantly craving for the feeling that 1 high gave them when they first experimented with the drug. They don't get it which is why heroin addicts eventually have to use it just to function. Without it they rattle and rather than spend 4 or 5 days in pain; it's easier just to score a tenner bag. It's pathetic really when there are children in this world that live with pain every second, every minute and every hour of their life's in agony. Heroin addicts are a cop out. Personally when I see one in passing; I want to vomit because I know what that addict is and has put their family and children through. 
The best piece of advice I can give is; let him go. You do not want an heroin addict around your son and why would you want an heroin addict around your son. It is no good for you or your son.
So he has left you for a fellow heroin addict? A woman it may be but she is a junkie so their relationship will be based around scoring smack. Heroin addicts love 1 thing and 1 thing only - which is heroin. I hope I don't sound harsh but it is a fact. You are absolutely far far better off without him in your life and your son is certainly far better off without him whilst he is using drugs. 
Please take note though; when his new woman finds a man who can provide her with more drug money; don't be surprised if he turns up at your door and I guarantee he will - when he is at his rock bottom. 
I am sorry you are going through this but your main priority right now is to take care of yourself and your young son. It may take some time; but you will get through this. It is his loss!