We generally operate under the assumption that we have limits, or ceilings, to our abilities and potentialities.
Do those limits really exist, or are they perceptual fabrications of our self-limiting minds?
Can we really get a little stronger than we were yesterday? Can we really improve our health a little more each day? Can we really progressively sharpen our skills a little more finely with the passage of time? Is it really possible to learn something new everyday?
Perhaps the only limiting factor (i.e., an answer of "no" to any of those questions) to our ability to "get better, every day, somehow, some way" is the time we have remaining to affect that improvement. Every moment wasted thinking that we've hit our limit is a lost opportunity to push those very limits.
The only limits are in our minds. We can think, act, and perform a little better each day, but only if we choose to.
"Onward and upward," to quote Reepicheep in the Chronicles of Narnia (C.S. Lewis, 1954).