When I did freelancing, I charged a bit more than I felt I should... but went above and beyond. My hourly rate may have been high, but I spent many "non-billable hours" making sure everything worked great and any changes (their fault or mine) were accounted for.

I did a few jobs where someone else controlled the billing, and kept us on a tight schedule. Every hour was billed. We were "fired" (AKA contract not renewed) every time. Yet when I went above and beyond, I had no problem getting and maintaining awesome clients.

As someone on the opposite side now (hiring freelancers), I've realized the thing I value most: the freelancer gives me less work, not more. It may seem obvious, but when I was on the other side, it wasn't. When I hire freelancers now, I value one overarching quality: to make my life easier. I don't care about price or hours (within reason), I care about not having to think about it.