“Some times your best effort just isn't good enough.”

Source: Norwegian Wood

Source: The Final Warning

Source: Safe Haven

The Almost Perfect State (1921)
Context: The best good that you can possibly achieve is not good enough if you have to strain yourself all the time to reach it. A thing is only worth doing, and doing again and again, if you can do it rather easily, and get some joy out of it.
Do the best you can, without straining yourself too much and too continuously, and leave the rest to God. If you strain yourself too much you'll have to ask God to patch you up. And for all you know, patching you up may take time that it was planned to use some other way.
BUT... overstrain yourself now and then. For this reason: The things you create easily and joyously will not continue to come easily and joyously unless you yourself are getting bigger all the time. And when you overstrain yourself you are assisting in the creation of a new self — if you get what we mean.

Source: The Dead Zone 1979