Well Pat, I'll tell you one thing: I'm glad that you made it through the night long enough to share with us today! It's clear that you've been through an extremely difficult night - sometimes everything just seems to come together simultaneously and pour all over you.
It's something that only those who have endured could understand, and even so, it's unique to every single individual. Nobody's "relapse" is the same. It's so important that you not only survived it, but recognized it early enough to take the next steps to move forward. It's something that you tragically saw happen with your friend... and by more than pure chance, you held on to the strength to carry on. You're still here for a reason.
Even though it may not seem like it, I want you to remember that you do matter. Yes, we can take the nihilistic view that nothing we do in this life matters in the grand scheme of the universe; but, on the other hand, our own little universe is all that we have. Your presence has undoubtedly impacted some other little universes out there in a positive way, a way that would not exist if you weren't around. I want you to remember that any time that you ever doubt your own relevance. Naturally, so that I'm not a hypocrite, I'll do the very same thing in such times. I'll count on you to do it, and you count on me.
Now, you mentioned all those various troubles that came together in mind. Are there specific ones that you can write about? Maybe that will help you work through them so that they won't suddenly bite the same way they did this time around.