No it's not but the complications caused by it can be. If you are willing to live a miserable life with a colostomy bag and tons of med's that make you feel like crap then no its not fatal. If you choose to live life on your own terms then it can kill you.
If you're still alive read "The Tibetan Book of The Dead" (I'm not Buddhist but it will provide you with a deal of clarity if you can see past the metaphors). I'm not a fan of platitudes but I think taking responsibility for yourself and living on your own terms starts by ending self-pity; death is invariably linked to it--you must let it go out of scope before you do.