Origin: http://www.uxmatters.com/mt/archives/2009/12/testing-your-own-designs-redux.php

The challenge in dealing with conformitory bias – “People can reinforce their existing attitudes by selectively collecting new evidence, by interpreting evidence in a biased way or by selectively recalling information from memory.” – is real. Getting “over yourself” and seeking out valid user testing and feedback is a tough call when you’re doing it all yourself, design and testing.

The points that Paul J. Sherman makes in his followup article that strike me most are these:

• Testing is not a Pass/Fail activity – it is a valuable element in the Design Process. Focusing the testing as a part of the path to a valid, usable solution is key.
• Test early, often, and as lo-fi as possible (keeping the initial investment, emotionally as well as in time/cost down).
• Usability testing serves design – use it to improve design.