Antonyms of fatigue :
freshen, refresh, refreshen, invigorate, relax, relieve, repose, rest, restore, recreate, bounce, dash, drive, energy, ginger, go, liveliness, pep, punch, sap, snap, starch, verve, vigor, vim, vitality, zing, zip, might, muscle, potency, power, puissance, strength, briskness, jauntiness, spiritedness, sprightliness, vivaciousness, vivacity, refreshment, rejuvenation, rejuvenescence, revitalization, decompression, ease, leisure, relaxation, amusement, dalliance, diversion, entertainment, recreation, sport, dormancy, idleness, inactivity, inertia, inertness, dallying, goldbricking, loafing, lolling, lounging, fun, play.
Examples of usage:
This latter had been carefully prepared beforehand by fatigue parties sent out from the battery at night. "Servants of the Guns", Jeffery E. Jeffery.
The mind cannot wear out, even if it can fatigue. "Seed Thoughts for Singers", Frank Herbert Tubbs.
Lord Parham lost more than he at all liked to lose, and at half- past ten he pleaded fatigue, refused to smoke, and went to his room. "The Marriage of William Ashe", Mrs. Humphry Ward.