I am also in the "charge enough" camp. When you are considering your hourly rate, remember that the hourly rate needs to cover your salary when you take holidays, vacations, or get sick (although as a self employed person you probably will not take vacations and work sick, but you should still ge paid for those days). Plus you need to have a retirement plan, FUND IT!!!
I also discovered that good customers feel better about paying more because they have more confidence in the contractor. Customers that are willing to pay better are the best customers, the keepers.
They also expect to be treated well, and they should be.
I also found that cheap customers are the most difficult to work for, so charge a profitable rate and they will go elsewhere, problem solved.
Do not fill up your schedule with cheap work, you won't have time for the very profitable job that needs to be done soon.
Don't let a smooth talking GC get you into financial trouble. They love to fund the project with your money by slow paying or not paying.
If I could go back and change anything, I think it would be to charge more. I understand that sometimes charging less is what it takes to get in a door, but I would suggest using a discount method (15% off coupon?) and keep your normal rates instead of selling a lower rate with no discount.
Best of luck to you!