THESAURUS
slip back
backslide, cock, degenerate, deteriorate, disimprove, fall, fall again into, fall astern, fall back, fall behind, fall from grace, get behind, get worse, go backwards, go behind, grow worse, have a relapse, jerk back, lapse, lapse back, let down, lose ground, pull back, recede, recidivate, recur to, regress, relapse, retrocede, retroflex, retrograde, retrogress, retrovert, return, return to, reverse, revert, revert to, sicken, sink back, slacken, slide back, worsen, yield again to