Not every action or emotion however admits of the observance of a due mean.
meanquotes
The proud man, then, is an extreme in respect of the greatness of his claims, but a mean in respect of the rightness of them; for he claims what is accordance with his merits, while the others go to excess or fall short.
There is no such thing as observing a mean in excess or deficiency, nor as exceeding or falling short in observance of a mean.
deficiency / excess / mean / observance
Mean is the cause.
By the mean of the thing I denote a point equally distant from either extreme, which is one and the same for everybody; by the mean relative to us, that amount which is neither too much nor too little, and this is not one and the same for everybody.