I would agree to a certain extend that life changing decisions come from ourselves.
A little luck is necessary to change our life. Or you might also call it fate.
Sometimes, out of the blue we meet good samaritans whom are of a great help to your progress, be it your career or personal life. This can occur by conversations with a stranger or by a friend's recommendation.
Being in the right place and right time also contributes to that one life changing experience.