Not that I'm likely to ever forget that I'm getting older, but just in case, my daughter (currently fascinated with the whole notion of age) provides me friendly little reminders from time to time.
Like this conversation last night, as I was making dinner.
Sweet Girl: Mommy, when will you be 39?
Mommy: Next March.
M: Because that's when my birthday is.
SG: (thoughtfully...) 40 comes after 39...
M: (sighing...) Yes, it does.
SG: Mommy, why doesn't 100 come after 39?
M: (laughing!) Because it doesn't. 100 comes after 99.
SG: Will you live to be 100?
M: I don't know.
SG: Why don't you know?
M: Because none of us knows how old we'll get to be.
Hmmm...takes "teach us to number our days and so gain a heart of wisdom" to a whole new level!