If you can inspect and analyze your own prior (using your own prior, of course) you can notice that your prior is not reflectively consistent, that you can come up with other priors that your prior expects to get better results. Humans, who are not ideal Bayesians but have a concept of ideal Bayesians, have actually done this.
(Though reflective consistency does not guarantee effectiveness. Some priors are too ineffective to notice they are ineffective.)
This might be a process of figuring out what your prior is, but the approximations along the way are not your prior (they might be some priors).
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.