That would be you.
Even if you're not self-employed, your boss is you. You manage your career, your day, your responses. You manage how you sell your services and your eduction and the way you talk to yourself.
Odds are, you're doing it poorly.
I'm amazed at how often people choose to fail when they go out on their own. Faced with the freedom to excel, they falter and hesitate and ultimately punt.
It's easy to spend your day at a job hiding from the real work, the stuff you actually get paid to accomplish. Easier to blame it on writer's block or on not being in the right frame of mind or on needing to keep up with Twitter.
(A great piece from Seth Godin's The Icarus Deception. p168)