Mia Vita is the Italian phrase for 'my life'. Occasionally you will hear the expression reversed to vita mia, often when the word vita is the direct object in a sentence.The first-person possessive pronoun mia is always feminine in this phrase, regardless of the gender of the speaker. This is because the pronoun must reflect the gender of the noun it is linked to.
Somewhat appropriately, the word vita has a deep-rooted and diverse etymological history - with its origins in the historical Indio-Aryan language Sanskrit, and in particular the word g'ivathasita. In time, the 'g' sound evolved into the voiced labio-dental fricative 'v' and was the precursor to the archaic Latin vivita. This eventually became the more familiar vita in late Latin and is the root of the word for 'life' in a number of languages, including the Spanish vida and the French vie.
As you can imagine, the exprssion mia vita is used quite frequently in Italian art, literature, film and popular culture. One example would be the 2011 film La peggior settimana della mia vita or 'The worst week of my life'.