Quittin' time

What compels people to just quit? Do we have these chemical reactions inside our brains that finally reach X-level for a particular thing and then we are just done? Sometimes when we quit, we do it in soft subtle ways. We just kind of drift off slowly but surely. Others are announced vehement and very noticeable what makes the difference in these scenarios?

When old people lose a life long partner, often they don't live 6 months to a year. They just lose the will to live. Seemingly healthy people slip away. Then, you have people who fight disease and death for long periods. Despite long odds, they go past any boundary given by doctors. Then one day, they make a decision. I'm done. Within hours or days, these people die.

I guess it's different for every person and each scenario. One person's quit level can be quite different from another.

OK, I'm freakin' rambling today. I had a point when I started, but I'm done. See you later. See, I just quit. lol