A very significant number of freelancers think of themselves as employees. They struggle with "asking for raises," instead of telling their clients "this is my new rate." They are extremely depressed when a contract isn't renewed, or is terminated early "they fired me. Why?" They are dependent on a single client, let themselves form close relationships with that client's employees, have their working hours set for them, etc.

Going into freelancing, the first thing you should be thinking is "I am a business that employs one person: me."