Firstly, You have to be creative and imaginative, as a freelance writer, you mostly own your time, which is expected to be spent wisely and creatively. Your mode of expression and communique must be different from a non-freelance writer who might not have the time and exposure as you. I know all kinds of writers need to be creative but if you're a freelance, I will expect more finesse from you, so drawing your write ups creatively all the time sure needs to be an habbit,.
You need to be daring, being a freelance writer will mean you will have to write about you're not even invited to write about, a lot of time, you will need to show yourself and your capabilities especially when you're still trying to make a name for yourself, you will need to write to people, about things, people, that you have little and much knowledge about.
You need to actually make writing an habbit, write all the time, get reviewers for your pieces, writing should be part of you, your writings it should be seasoned.