There are quite a few places where the author uses the expressions ‘my heart sank’, ‘panic seized’ etc. What was the reason for this?

In “The Luncheon”, the expression “my heart sank” has been used by the narrator when the lady ordered caviar in the restaurant and the narrator was trying to estimate the cost of the dish. He has employed this phrase to express his inability to afford the dish. The narrator has also used the expression “panic seized” to state his anticipation by wondering about the price of the dish and whether it would exceed his budget line. Both the expressions lend humor, pathos, an embarrassment to the situation.