Why not ask your customers what they think about your products? Try doing this every six months and ask them what they think are the good and bad points. You can contact them by email or at the events you attend. Conduct market research to see what you should change. Then take action!
Not only is this a good way of improving your products, but it makes your customers feel that their opinion is valued and they are more likely to want to do business with you.
Whilst you might want to please all the customers you have conducted market research with, you don't have to. If a customer has stated that they would like something that will take hours and hours and hours to make, but they wouldn't be willing to pay the price for your time - then can you afford to do it? If you're trying to turn your hobby into a business, then the answer must clearly be a resounding 'no'.
Customers and projects which are causing you sleepless nights should be reviewed and you should decide if you want to put yourself under that pressure.