Guys what is the limit of interfering in each others' lives?

he has depression, blaming himself, really in a struggling job blah blah.. he drinks a lot, gambling and paying credits because of that, have some dark friends... also divorced and sometimes it seems to me that it is normal, as I cannot forget my ex (and my first) sometime.. I wanted to talk to him that he has to pay attention to his own life and health.. he responds not good.. he is not a looser all the time but very close when he is under deep pressure.. should you warn him? or what is your recommended action on this?
Guys what is the limit of interfering in each others' lives?
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