On the adjustment that never stops
“A man can be himself only so long as he is alone.”
Schopenhauer means this bitterly. For him other people are principally a tax, and the sentence belongs to a long case against company as such.
The observation underneath survives his mood. In the presence of others some adjustment is always running — a small continuous editing of what you say and how you sit. It is not dishonesty and it is not avoidable. But it costs something, and he is right that only being alone switches it off.