Suddenly, you're in your mid-twenties and contemplating marriage, children, mortgage payments, car payments, student loan payments and smile because this is what you wanted to achieve.
The kids graduate high school and go off on their own adventures, leaving you with a bit of empty nest syndrome, but you learn to adapt...and cherish the times when those kids come home and laughter and fighting once again fill the house.
Now you have grandchildren, possibly more silver hair, it isn't as easy as it was 25 yrs ago to get around, but you do it. You stay active and you play with those grandchildren, knowing your remaining time is precious and you must do whatever you can in the last good days you have to be a positive influence in their lives and in the lives of those around you.
You look ahead...now you may only have 15-20 years left to live. Yes, we all die, it's just how it works, but where did the past 50 years go? What happened? Why does time pass so quickly?
My advice to you is, stop thinking about how much time you have left and start doing what you want to do when you want to do it. Make sure that you leave no stone unturned, that you have no regrets, that you have your end of life plan in place so your kids don't have to scramble, wondering what your last wishes are.
Have fun! Sit outside and turn your face to the sun and thank your Creator for the wonderful life you've lived and the days yet to come.