With freelancing you never know when the gig is going to end. With freelancing, you never know when the gig of your dreams is going to pop up. With freelancing, you never stop hustling.
It's like any other business. When you are your own business, you need to keep an eye out for new clients and opportunities to grow.
Growing doesn't necessarily mean more work. Some of the leaders in the field say that if you're working constantly 50 - 60 hours a week to break even you're doing it wrong.
Writers, whether they write for trades, magazines, newspapers, blogs, corporations, etc., always have to look to expand their connections within their industry. Keeping in contact with industry folk allows you to gage the market and find ways to set yourself apart from the rest. It keeps you in line with the latest developments and will definitely help you develop fresh ideas and angles.
Resting on your laurels is never a good idea.