life-altering       
adjective uk/ˈlaɪfˌɒl.tə.rɪŋ/ us/ˈlaɪfˌɑːl.t̬ɚ.ɪŋ/ (also life-changing)
 改变人生的
having an effect that is strong enough to change someone's life
  The birth of a child is a life-altering experience. "孩子的出生是一次改变人生的经历。 
 His time as a young doctor was life-altering. 他年轻时当医生的经历改变了他的一生。 
 - More examples
 - I had to write an essay about a life-altering event.
 - She's a 15-year-old kid who has to make a life-altering decision in less than 15 minutes.
 - Only someone who's lost a child can understand the life-altering, all-consuming grief.