Your body breaks down, it just does, though I suspect FA hastens the breaks.
Baseball pitchers, for instance, might lose some velocity on their pitches. Good ones adjust, maybe becoming more like Jamie Moyer, who never had velocity but pitched until my age and won 269 games with smarts.
Like Moyer, I have plenty of smarts, and my super-awesome physical therapist has given me even more.
I don't use it, though.
I know that to transfer safely, heels need to go behind knees. That way you can use your leg muscles then and your knees come unlocked easily.
I can do this with my right leg, but my stupid left foot slides forward when I try.
The upshot is I don't try. I rely on what I have always done: I set my chair so a wheel blocks my left foot, then I use my arms and right leg to stand and hope I can unlock my left knee.
This transfer -- to my chair -- accounts for the lion's share of my falls.
If I were a pitcher, I'd get pummeled.