The nutshell is I don't particularly care to die, but I don't have anything special (skill, attribute, object, person, whatever) to keep me going. I had a nice time this life, but the thrill is lost and it's been years since it has seemed worth while and I'm looking for a valid reason to continue existing and finding none. I don't expect I will read an answer here. But what the hell, gimme your best suggestions.
Actually, I think there is a "particular internal drive", it is called self preservation which seems to be shared by all species. It is rather odd from an evolutionary standpoint that humans can over come their natural drive to live and commit suicide.
Some whales do that. It's uncommon, but not unheard of.
Curiosity.
I agree with you. Curiosity cranks me up everyday and the certain knowledge that the world would be a more boring place without me.
I lost most of that, at least the passionate variety. I agree with Spin about the world being more boring without me, but there's plenty of entertaining people to go around and in short order, any given one of us won't be missed by many or by much. The world would still spin and life would still go on for the people with the zest to live it. And they're welcomed to it, here don't let me waste the air and nutrients others could use to better benefit and step aside...