When you hold your breath the ongoing accumulation of carbon dioxide in your cells, in your blood and lungs will eventually irritate and trigger impulses from the respiratory center part of your brain. Rising levels of carbon dioxide signal the body to breathe and ensure our unconscious and autonomous respiration.
The Brazilians celebrate the Valentine's Day in a very big way. Unlike in the United States or any other countries, Brazil does not celebrate Valentine's Day on the 14th of February because it usually falls close to the Brazilian Carnival. They celebrate the Dia dos Namorados (Day of the Enamored) on June 12th.
The then Pope, Gelasius, declared 14 February to be St Valentine's Day, a Christian feast day. This is likely to have been an if-you-can't-beat-them-join-them approach to the still-popular pagan festival of Lupercalia.