Synonyms and related words :
become suicidal, come down, decline, degenerate, despair, despond, deteriorate, die, droop, ebb, fade, fail, fall, fall away, fall off, give way, go down, go downhill, go off, go to pot, have a comedown, hit a slump, hit rock bottom, hit the skids, languish, lapse, lose heart, plumb the depths, reach the depths, run down, sink, slide, slip, slump, subside, wane