Change, Death.

I was reading a friend's blog and came to the realisation. (Ok Aeon Flux helped too)

Change is what makes life worthwhile. Knowing that situations will end and change makes the situation either more bearable (if it is bad situation) or more valuable (if it is good situation.)

A great situation that lasts forever is definitely less valuable than one that lasts for short time because you'd cherish it. Because you know that it might just end.

What makes life worth living, is that one day you will die. It makes you realise that every moment counts, whether or not you use it. So use your time wisely.