If you're 15, be thankful that you're indestructible and have absolutely no concept of your own mortality.
If you're 20, be thankful that you're not yet feeling random aches and pains - that begins around 25.
If you're 25, be thankful you're not 30 - that's when people start to think they're getting old.
If you're 30, be thankful that you're still on the far side of 40, and avoid the stigma.
If you're 35, be thankful you're not 40 yet, and continue to avoid the stigma.
If you're 40, be thankful for everything you've accomplished so far, and think about how far you are from 50.
If you're 50, be thankful for your grown children and the lives they're starting, and smile as you monitor your investments.
If you're 60, be thankful for all the money you're about to rake in if you've played your cards right for the last forty years.
If you're 70, be thankful for all the fun you had in your sixties.
If you're 80, be thankful that you've lived beyond the average human age.
If you're 90, be thankful that you have a shot at the century club.
If you're 100, be thankful for that number and also be optimistic - at this moment, there are more than 50,000 of you and you're the fastest-growing segment of the population and your lives are of higher quality than ever before for people your age.
If you're 110, be thankful that you may set a Guinness record.
If you're 120, be thankful that you're alive, as opposed to the alternative.
My point here is that for a decade, whenever I griped about being whatever age I was, I quickly realized that not only were there people older than I was, but they had it good too. If there's ever a reason to complain, just be glad you're not ten years older. Also, these are just numbers - I dealt with turning 30 by exercising and eating healthy and I ended up in better shape at 30 than I'd been at 25. Words can't capture how good that felt.