When you ask Millennials why they love the job that they do, they are likely to tell you that they are passionate about it. This is sometimes accompanied by a story of when they had a job that was miserable for them, and then they had a revelation that lead them to leave that terrible job and start their own underwater basket weaving co-op.
But overall, most people who are highly satisfied with their careers have more than just something that they are passionate about. They have autonomy, they feel competent, and they get along well with the people they work with.
And, most importantly, they have a job that supports the life that they want to live.