As an independent unit of life, man faces two limits: that of body and that of mind.
Any instance of human activity ceases either because of a hard biological limit (I broke my arm therefore I cannot paint), or because the discomfort becomes too great (no one is buying the paintings therefore I shall not paint).
The latter is a soft limit that can be stretched through training (perseverance can be learned: maybe I should continue painting anyway?).
However, if the soft limit stretches so far it meets the hard limit, you get the bodily smack-down of madness or illness: you will go no further.
The difference between the soft and the hard limit is measured in effort.
A personal anecdote
A long time ago my high-school sociology teacher delivered a blow to my pride that set me in my place for life. I had asked him for a reference. He wasn’t too worried about keeping what he wrote a secret, indeed, he encouraged me to look at the form, right there, in front of him.
Only one point surprised me: he’d scored me 4 out of 5 on “General Effort”.
Tell me my facts are wrong, tell me my form is poor, but how dare you tell me I didn’t try to the utmost of my ability?
I brought this up in diplomatic tones, and I witnessed the first and so far only instance of someone’s eyes glinting.
Then a grin.
Then he said: “Well, if you’re honest with yourself, do you try as hard as you could be trying?”
You only get so many of those self-searching moments where circumstance, mood, and honesty join in a bitter-sweet union. This was one of them.