You have changed my life.
mi AI cam-BIA-to la VI-ta — stress on 'bia-' and 'vi-'. 'Cambiato' has three syllables: cam-BIA-to.
A profound declaration — this person's arrival has transformed who you are and how you live. Said with deep sincerity.
'Mi hai cambiato' = you have changed (passato prossimo of 'cambiare'). 'La vita' = the life (with definite article — 'my life' expressed through the indirect object pronoun 'mi'). In Italian, this construction with 'mi' + definite article replaces the possessive adjective in many body/life expressions.
Da quando ti ho conosciuto/a, tutto è diverso.
Since I met you, everything is different.
Before/after — their arrival created a new chapter in life
Sei entrato/a nella mia vita e l'hai trasformata.
You entered my life and transformed it.
'Trasformare' is stronger than 'cambiare' — total transformation
Non sono più la stessa persona da quando ci siamo conosciuti.
I am no longer the same person since we met.
Personal growth through love — the relationship has changed who you are
Italians believe love should be transformative — 'l'amore cambia' (love changes things) is a cultural truth. A love that leaves you unchanged is considered insufficient. The willingness to acknowledge and name this transformation is a sign of emotional maturity and depth.