There's no doubt that the ageing process is horrible.
I am early 30's and it took until age 30 to start thinking about my future health. When you are in the teens and twenties you think you're just going to live forever.
It helps to know that some people make it to their 80's and are in really good health! There are some strong, fit 80 year olds out there, telling yourself that you may end up like one of them can make you feel a bit better. And keeping an eye on your health now might help you later!