go to pot, go to the dogs - become ruined; "His business went to pot when economy soured"

delapidate, decay, crumble - fall into decay or ruin; "The unoccupied house started to decay"

wear off, wear thin, wear out, wear - deteriorate through use or stress; "The constant friction wore out the cloth"

fatigue, jade, tire, weary, pall - get tired of something or somebody

languish, fade - become feeble; "The prisoner has be languishing for years in the dungeon"

rot, waste - waste away; "Political prisoners are wasting away in many prisons all over the world"

decline, worsen - grow worse; "Conditions in the slum worsened"