..."because someday I won't be able to do this anymore"...
I used to run. I ran everything from the 50 yard dash to marathons. I ran in the flats and in the mountains. I loved it and I thought I could do this forever. Then at age 57 a knee injury ended my running career and I could not do this anymore.
I ride now. I love it. I will ride for as many years as I can.