A Mortal Thought: so many of us long for immortality. To live forever, for infinity - time enough to get everything we can imagine doing done.
But here's the thing about infinity: it's not as "everything" as you might expect. Take the simple counting numbers... 1, 2, 3... there's an infinite number of them! They go on forever. Everything you could possibly dream of, right?
Well, no. There are more infinities lurking. Now think about how many numbers fractions are between 0 and 1... 1/2, 1/4, 3/4, 1/8... 311/782, 612131/981141, etc etc etc... there's an infinite number... all lurking between 0 and 1. And the same number must be lurking between 1 and 2, 2 and 3, etc. (And don't even get me started on the decimals... there's an even bigger infinity of them than the fractions, it's a long story)
So even if you had an infinite number of days to work with, there'd be things you couldn't get done - possible paintings you couldn't make, potential books you couldn't write, fabulous romances you couldn't pursue. The space of the possible blossoms and expands far further than our linear selves, even if our linear selves were going to last forever.
I find that reassuring. Sure I'll be missing out on whatever happens after I die, and I'd love to have quite a bit more say in when that happens. But even if by some miracle I managed to live forever without getting bored out of my skull (see the final chapter of Julian Barnes' "A History of the World in 10 1/2 Chapters" for an exploration of that theme) there would still never be time to do EVERYTHING...
(In response to a response to the above)
One thing I didn't get into - I know my life is influenced by Objective Shoulds - that "objectively" it would be better to accomplish this, learn that, achieve the other. But I find it useful to remember that I don't actually believe there's any external authority determining that... so I don't have to worry about what potential goals I don't make nearly as much as I do.
I'm imagining that if your goals are more self-realized, that there are things you'd want to get done because YOU would want to, and not how other people or "objectively reality" will judge you - well, I guess this outlook is less help... the commitments you have to do and the choices of things you prioritized might well be blocking other things/classes/places/connections/reconnections you'd like to do, and so the best we can do is look for silver linings, try to prioritize and push and make a little time for that secondary but rewarding stuff...