Is there a moment in the day or in one's life where every hidden feeling inside one's self is revealed unintentionally?

For example, when a depressed person is always smiling in front of other people to hide his depression, or a lonely person acts friendly and in a lively way to hide his loneliness, suddenly gets his depression or loneliness revealed unintentionally and without this person’s awareness, as if the mask that person was wearing melted there for a moment… Is there such a moment? Does it exist?

And if there is such a moment, when would it be?