Utmost; highest endeavor or state; most nearly perfect thing, or being, or action; as, to do one's best; to the best of our ability.
Webster, Noah, Webster's Unabridged Dictionary—(2n...(2012)
It remains only to do one's best, and endure with patience what God sends.'
Leyland, Francis A., The Bront? Family, Vol. 2 of 2—with...(2011)
Well, well, one can only do one's best.
Lever, Charles James, Tom Burke Of "Ours", Volume I(2010)