(one's) mission in life
The ultimate goal or purpose toward which one strives; one's reason or motivation to continue existing, operating, or working. Top-notch customer service is our mission in life, so if you are unsatisfied with your experience with us, we will refund 100% of your payment. Bruce's mission in life has been to serve justice to those who evade the law.
mission in life
one's purpose in life; the reason for which one lives. Bob's mission in life is to make money. My mission in life is to help people live in peace.