Yes, it's harder as you get older but if you grit your teeth you can still do it. I celebrated my 64th birthday this summer. I have gout, arthritis, two fingers missing, high blood pressure, angina and rotator cuff damage/pain in both shoulders, but by God's grace I am still going. Recent hurricane induced floods felled this big Red Oak that I've started cutting up - about three cords. After it's done I have to plant this field. I've roofed our house this spring and summer after winds tore part of it off. 26 squares all by myself (lots of gritted teeth). My wife suffered a heart attack this spring to boot.
Hard? You bet, but I ain't dead yet. This is the Oak before I got started cutting. There was an ugly little cottonmouth on one of the limbs about 4ft. off the ground.
You can do it! Just stop to rest often, or take a nap then go again!