Ok, I have to be serious here. I'm old enough that I could make it another six minutes or another six years or another 20 years. But I if I dwelled on that I would be a miserable old woman nobody would want to be around. Life isn't about fearing it, it's about living it. None of us no matter our age knows how many days or weeks or months or years they have left but it is a fact that if you take care of yourself you will live a more active and productive life. I've not been a shining example of taking care of myself but I do try to stay as active as I can. For my age I do ok but of course I wish I could still do what I could when I was 21.
I didn't think about it much when I was that young other than many of my friends and family my age were dying in a war. So I thought I probably wouldn't live this long and thus I decided to live every moment of it.
There are so many adventures out there waiting to be had, so much to learn, so many places to see, chats to have, people to love, friends that are strangers you haven't met yet. Live for today, go do something different and don't dwell on something you have no control over other than to exercise, eat well and learn to deal with stress.
I love being old. I love having learned to love who I am (I think that ability comes with age). I love how I have learned to slow down and take time to appreciate the beauty and laughter life offers instead of dwelling on beating my head against a wall trying to change things that can't be changed (like getting older). It's a good trade off, arthritis slowing me down but the knowledge to split wood in a way that isn't so difficult or instant recall for not only not caring about what someone else thinks about you but not remembering it either.

Set some goals and set them high and go out to achieve them. Give yourself time limits to achieve those goals. Not only will you be too busy then to worry or dwell on getting old, you will make getting old more comfortable by achieving so many goals in life. Try it, it works.