John Lennon told George Martin, one year before he was murdered, that he wishes he could have re-recorded most Beatles songs, as he felt they could have been better. When asked about Strawberry Fields, for which Martin said he bled to make it a masterpiece, Lennon replied..."especially Strawberry Fields!"
Most artists are extremely critical of their own work and often disappointed by their efforts. Human nature, I guess. If your clients love your work, and you have done your best to give them what they wanted to make them happy, then you should feel good about your efforts and not guilty for proper compensation. It's always good to wanting to do better, but it sometimes takes a toll on ourselves and makes the creative process a lot harder.