"And you are the easiest person to fool"
Richard Feynman, the well-known American physicist and Nobel laureate, famously said: “The first principle is that you must not fool yourself -- and you are the easiest person to fool”.
These words really stuck with me.
As someone who did relatively well in academic contexts, it's really easy to let that develop into a sense of invulnerability to being wrong and deafness to contrary opinions.
It's also easy to reach out to some misguided sense of authority, rest on the comfort of past achievement, and to let believe it is in some way inherent to yourself.
Reality is the ultimate check.
What's the hypothesis? What's the distillable observation, were it to be true? Did the actual results hold up to the expected outcomes?
We fool ourselves into believing we always proceed logically like this.
For all of these steps to actually take place they must happen outside of our heads, in some recorded medium.
After all, there must be a fair chance to be wrong, if we'd ever like to claim we were right.
Only when the method is specified and chain of reasoning is laid out in the open, it's possible to judge the weight of the claim and the soundness of the conclusions.
It's then possible to realize in what way were you wrong, learn from it, and do better next time.