The master leads you to the door; the rest is up to you.
Tips
culture
修行 is central to Buddhist and Daoist traditions. The famous proverb 师父领进门,修行在个人 emphasizes that a teacher can only guide — true progress depends on the individual.
usage
Can also be used loosely for any dedicated practice or self-improvement, not just religious cultivation. E.g., 做饭也是一种修行 (cooking is also a form of practice).