Related to: Tsuyoku Naritai! (I Want To Become Stronger), Test Your Rationality, 3 Levels of Rationality Verification.
Robin and Eliezer ask about the ways to test rationality skills, for each of the many important purposes such testing might have. Depending on what's possible, you may want to test yourself to learn how well you are doing at your studies, at least to some extent check the sanity of the teaching that you follow, estimate the effectiveness of specific techniques, or even force a rationality test on a person whose position depends on the outcome.
Verification procedures have various weaknesses, making them admissible for one purpose and not for another. But however rigorous the verification methods are, one must first find the specific properties to test for. These properties or skills may come naturally with the art, or they may be cultivated specifically for the testing, in which case they need to be good signals, hard to demonstrate without also becoming more rational.
So, my question is this - what have you become reliably stronger at, after you walked the path of an aspiring rationalist for considerable time? Maybe you have noticeably improved at something, or maybe you haven't learned a certain skill yet, but you are reasonably sure that because of your study of rationality you'll be able to do that considerably better than other people.
This is a significantly different question from the ones Eliezer and Robin ask. Some of the skills you obtained may be virtually unverifiable, some of them may be easy to fake, some of them may be easy to learn without becoming sufficiently rational, and some of them may be standard in other disciplines. But I think it's useful to step back, and write a list of skills before selecting ones more suitable for the testing.
Both my husband and I have cognitive challenges (don't we all, we imperfect results of evolution, us) that constantly threaten to sour our relationship. We strongly credit our study of cognitive science and rationality for keeping our relationship sane and enjoyable. We make conscious decisions about how we manage our moods relative to each other. We work hard to recognize cognitive biases and to tease out objective fact from fallacy. We have a very strong, twenty year relationship because of that.
Then again, one of the things that attracted each of us to each other was the fact that we were both rationality-seeking and valued that in the other. I believe, however, I can make a rational case that our approach towards mutual anger management, anxiety management, and so on, has helped our relationship to remain strong, fruitful, and enjoyable.
For certain, understanding the philosophy of science -- minimally, the concept of "confounding variables", along with other concepts and practices -- has helped us get and keep my husband's bipolar in control. For about a year he was hallucinating due to some medication imbalances. His understanding of experimental methods and rational thinking helped him differentiate hallucination from reality during that period. Our understanding of science has also helped us make some pretty good decisions about our health, and even about our dog's health (the little tyke is 17).