One of the biggest challenges in our lives, in my opinion, is how remind ourselves, every day, that this is the only life we get (or for those who believe in the afterlife or reincarnation - that this is the only life we get to our knowledge!). Most of us act as if our lives will go on forever and concentrate on what's in front of us which is mostly irrelevant in the grand scheme of things.
The challenge as I see it is to remind ourselves daily that our lives will one day end and that we should make the most of them while we still can. It's that sense of true perspective which we miss on a daily basis.
I'm toying with the idea of designing a coloured wristband (similar to Lance Armstrong's Live Strong wristbands) which might act as a daily reminder of our own mortality.
Imagine the things you would do, imagine the fear you'd lose and imagine the love you'd show if you kept that thought ever present in your mind.