comedown

letdown, blow

Synonyms: anticlimax, blow, collapse, comeuppance, crash, cropper, decline, defeat, deflation, demotion, descent, disappointment, discomfiture, dive, down, downfall, failure, fall, flop, humiliation, pratfall, reverse, ruin, setback, undoing, wreck

Antonyms: ascent, boon, boost, fortune, promotion

After many years as a minister, teaching was a bit of a comedown for him.