relapse

nouns

a failure to maintain a higher state
backsliding, lapse, lapsing, relapse, relapsing, reversion, reverting

verbs

deteriorate in health
"he relapsed"
get worse, relapse
go back to bad behavior
"Those who recidivate are often minor criminals"
fall back, lapse, recidivate, regress, relapse, retrogress
is derived from
relapsing