To slip or slide back, in a literal sense; to turn back.
To slide or turn back into a former state or practice; to fall back from some condition attained; -- generally in a bad sense, as from a state of convalescence or amended condition; as, to relapse into a stupor, into vice, or into barbarism; -- sometimes in a good sense; as, to relapse into slumber after being disturbed.
To fall from Christian faith into paganism, heresy, or unbelief; to backslide.
A sliding or falling back, especially into a former bad state, either of body or morals; backsliding; the state of having fallen back.
One who has relapsed, or fallen back, into error; a backslider; specifically, one who, after recanting error, returns to it again.
Great effort is required to arrest decay and restore vigor. One must exercise proper deliberation, plan carefully before making a move, and be alert in guarding against relapse following a renaissance. Horace
The other thing is that if you rely solely on medication to manage depression or anxiety, for example, you have done nothing to train the mind, so that when you come off the medication, you are just as vulnerable to a relapse as though you had never taken the medication. Daniel Goleman