"If you want to arrive at the conclusion that the good man ought not to get drunk: Tell them of all the things men do that they would blush at sober, that drunkenness is nothing but a state of self-induced insanity. For imagine the drunken man's behaviour over several days: would you hesitate to think of him out of his mind? As it is, the difference is simply one of duration, and not degree." ~ Letter LXXXIII
However it is not just the drunken mind which we would ought to attribute insanity:
If we met a man who was constantly enraged, much like the Hulk, would we hesitate to think him out of his mind?
If we met a man who was constantly afraid, a state of constant anxiety, would we hesitate to think him out of his mind?
If we met a man who was constantly jealous, exercising continual obsession, would we hesitate to think him out of his mind?
Even euphoria. If we met a man who was constantly elated, would we hesitate to think him out of his mind?
These emotions are not entirely bad: anger can be righteous, fear - protective, and who doesn't want euphoria? The issue is when these emotions become prolonged, extreme and irrational. Rage, resentment, and anxiety deprive us of reason.
I like this frame. Viewing my rage, fear, jealousy and even euphoria as temporary lapses of rationality and reason restores my control. Remember the next time you feel one of these things, perhaps the only difference between you, and a mad-man is just the duration of your emotion and not the degree.