your work is not how much you value you it. it is always what the customer is willing to pay.
I don't agree with this. You see, if you say that your work is shit and you really believe that, then you will probably talk to the client in a way that subconsciously you will make him believe that your artwork is shit. And then the client will say "wait a sec, why am I buying this shit from the guy that says that his own work is shit?"
Dont ever let money stop you from doing what you like to do.
I really agree with this.