Let me relate a personal anecdote from my using days that shows the limits to how much you can help someone. I knew this chipper who, despite not being addicted, was the most irresponsible user I have ever met. It was well-known from others who had used with him, that he would use as much heroin as he possibly could. Not surprisingly, the first time he used around me, he overdosed. It was not particularly bad. I managed to get him conscious quickly and made him swallow a naltroxon pill--partly because I was still a little concerned and partly because I wanted to punish him, since I had warned him not to do the amount he did.
On the second occasion it was much worse. He stopped breathing. I had to give him mouth to mouth resuscitation several times over the course of the half hour that he was unconscious. Again, I had told him he was doing way too much, but he did not listen (I later found out that in addition to doing all of his, he had stollen some from me). As I drove him home, I told him that he was not welcome around me ever again. As it turned out, that was the last time I saw him.
Maybe this was callous. But there is only so much you can do for some people. I had done what I could for him--including saving his life--but he would not accept my help when he was conscious. About a year later I found out that he had died of an overdose--either because he was alone or because he was with someone who couldn't or wouldn't help.