It's an Aristotelian slogan that virtue lies in the middle, between the extremes. Courage, for example, is found between the extremes of cowardice and foolhardiness. But it's not a mathematical middle. It's somewhere in between. A lot depends on the context. Hence, the cardinal virtues are courage, justice, moderation and prudence.
I overheard a conversation a while ago at my deceased gym. A twenty-something trainer, one of the finest pieces of eye candy my bifocal-wearing ocular globes have seen in a while, was chatting with his client about politics. He opined that it was a mistake to be either conservative or liberal, since neither side ever got what it wanted. That makes you unhappy. So he wanted to be in a comfortable place somewhere in the middle, where he would not be constantly dissatisfied. A handsome young Buddha in a leather jockstrap! (A pic is here, if scroll half way down, on the left.)
On the level of comfort and daily ease, I wish I could follow his advice, not notice or care about the situations that irk me, be content with things as they are, with people as they are, with me as I am. This is not a setup for me to proclaim that because I am not satisfied with how things are that I am therefore and for that reason virtuous. Even if I am right about the things that get to me, that does not translate into making me virtuous. Merely correctly dissatisfied.