Paul Graham puts life and child-rearing into perspective in his post Life is Short:
Having kids showed me how to convert a continuous quantity, time, into discrete quantities. You only get 52 weekends with your 2 year old. If Christmas-as-magic lasts from say ages 3 to 10, you only get to watch your child experience it 8 times. And while it’s impossible to say what is a lot or a little of a continuous quantity like time, 8 is not a lot of something. If you had a handful of 8 peanuts, or a shelf of 8 books to choose from, the quantity would definitely seem limited, no matter what your lifespan was.
It reminds me to continually re-focus on the things that matter—whatever those things may be: children, family, relationships, career—and to not let anything else steal away those meaningful moments.