WordNet sense 1 (pass by):

elapse, pass, go by, slip away, go along, glide by, slide by, slip by

WordNet sense 2 (pass into a specified state or condition):

sink

WordNet sense 3 (drop to a lower level, as in one's morals or standards):

backslide

WordNet sense 4 (go back to bad behavior):

regress, relapse, retrogress, recidivate, regress, relapse, fall back

WordNet sense 5 (a mistake resulting from inattention):

oversight

WordNet sense 6 (a failure to maintain a higher state):

reversion, backsliding, lapsing, relapsing, reverting