Why is the Eightfold path called the Middle Way?

In this sutta, the Buddha describes the Noble Eightfold Path as the middle way of moderation, between the extremes of sensual indulgence and self-mortification: Monks, these two extremes ought not to be practiced by one who has gone forth from the household life.

Explanation:

which time period is this? or is this story fictional, i'm going to need more info to answer this question