'Mindig az a perc' - Ever that moment. Here is Wiki on Karády. To summarise: born very poor, started acting in 1936, became the leading glamorous film star through the war. She was arrested in 1944. Having been charged with spying for the Allies, she was imprisoned, tortured and almost beaten to death by the fascists. Nevertheless because she had been popular in the Horthy era her life became very difficult under communism. Her films were banned and her acting career forced to the very margins. In 1951 she left the country. She lived in Brazil and the USA and never returned. Died in 1990. She was given a posthumous medal by Yad Vashem in 2004 as a righteous gentile.
The first verse of the song translates (translated pretty impromptu by me) as:
The loveliest moment is ever the one
that life will never grant you;
The most wonderful kiss is the one
that we will never enjoy;
The most marvellous dream is the one
that most quickly comes to nothing,
it is the dream we never dream again.
It is, of course, a sentimental song, but then many of the songs of the time were, partly because times were hard and dangerous and the words were likely to be proved true. But the sentiment is often accompanied by irony, acidic wit or playful lightness of heart.