This is the 18069th most frequent Polish word.
życia
"Życia" means "life" (genitive singular or nominative/accusative plural form) in English.
Here, 'życia' is used in the genitive case to denote a quality or aspect of life.
Kocham spokój życia na wsi.
I love the peace of life in the countryside.
In this sentence, 'życia' in the genitive case specifies the origin or subject of the lesson.
Najważniejsza lekcja życia to być szczęśliwym.
The most important lesson of life is to be happy.
In this example, the genitive 'życia' denotes possession, relating to the speaker's life.