I have felt that way pretty much my whole life. Considering I'm working on antiquity it has been a long, long time. I've had so many yesterdays that I guess it just doesn't matter any more.

When young, you open your door in the morning and see what lies ahead. It might be crappy but it still is ahead. Then one day you open your door and realize nothing lies ahead. What happen to all those days that use to be my future?

As a frog of little brain I have no answers for you but I assure you, you are not alone.
kebs