One big unwritten rule in the entertainment industry: Never sell yourself short. Same with you @steevc.
Picture yourself strumming a guitar in the park. It's Saturday, busy day, people everywhere. They're dropping change, a few bills, enjoying your performance. Are you counting the money as it rolls in? Are you going to stop mid-song because you've earned your quota? Then you go again the next Saturday. You earn more. Then you go again the next weekend, and earn less. Did you earn too much on the best day? No. You did your thing, and whatever happened, happened.
Would someone who released their first album expect to go platinum? If they did, would they say they earned too much?