Jason had had what seemed like an unbeatable, untreatable addiction to, alternately, heroin and oxycontin. It was a heartbreaking, trying and puzzling five-year stretch for me, so I can't imagine how bad it was for him (well, that's not entirely true. Mewes would periodically flash self-awareness with statements like "If I'm still like this when I turn thirty, I should probably kill myself.").
This is a great essay/blog series about Jason's descent into drug addiction and his struggle to return. You can feel the how frustraiting it was to deal with him, and how much dispare he caused for the people that loved him. You can also see that Kevin Smith's wife put up with WAY more shit then most people would have.
My only complaint was how long it took Kevin to post it. He dragged it on and on... each time ending it as a cliff hanger.