Increase Your Margin of Error
Your body is an adaptive system. No two bodies are the same because they have all adapted to different stresses placed on them. Cyclists develop big quads, and rowers develop the shoulders and arms. Your body is strengthening in response to stress and atrophying from disuse.
The upside to this is that if you can keep the various parts of your body mildly stressed you can keep your body in a state of global improvement, where all parts are getting better simultaneously.
The downside is, if you are like me, probably do not have much of what engineers call a margin of error. The margin of error of your body is how far you have to challenge it beyond your normal routine before some part of the system fails. Your body is always adapting to your environment, and it works to minimize the energy expended. This was great for your ancestors who could eat fewer calories because the muscles they did not need were not getting big. But not so great for modern you living in a calorie-rich environment.
This adaptation means your body becomes just barely good enough to handle the maximum stresses placed on it throughout your routine. On my path to increasing my overall physical fitness, I had a few moments when I realized some routine task in my life was a lot easier than it used to be.
My wife and I do not sleep in a bed. We sleep on a mattress on the floor. When we get up, we go from squat to stand. I never thought about this motion being difficult for me, but once I had developed my squatting strength, I noticed I could much more easily get out of bed. On the flip side, before I started working on my squatting muscles, I was on the verge of not being able to get out of bed!
I have noticed similar situations when balancing on one leg to put on my shorts, easing myself down onto a toilet seat, and picking up my wife while hugging her (she wants me to say it is all due to her weight going down).
All these routine actions had such a low margin of error, that I was always living on the edge of making one stressful move that would lead me to fall or hurt my back. You may think you are far away from the old lady you see using a walker, but I am afraid that most of our margins of error are so small that we are not far away from that at all.
Let us build our margin of error in our daily activities. By putting short but intense stresses on all of the parts of my body, I believe I will continue to build my margin of error. Constantly listen to your body and look for where your margin of error has gotten too thin. You will know when it happens, it is called pain.