Our memory tends to contain less and less information. We forget certain things, and our memory about others become simplified, and a complex article boils down to “X is bad, Y is good, try to do better".

One unexpected consequence of this is how it impacts our sense of probability: to describe the probability binary, it only requires 1 bit of information, but to describe the probability as a percentage, you need a lot more bits!

Because of this, a person's confidence in the most likely hypothesis in his opinion tends to 1 over time, and the probability of all other hypotheses that he had time to think about tends to 0. Every time he remembers a hyp, a person will less and less often remember the nuance that “the probability of hyp A = X”, he will simply remember “And this is the truth (that mean the probability of A = 100%)”.

(Edit: it works this way for some people only. Others understand that just because they remember something as "true," it doesn’t mean their past self believed it with 100% certainty. I wrote this article to everyone do like "others")

Another way certainty in a hyp may grow over time is when we forget its weak spots—the things we should think about to test it.

I’ve often found myself in a cycle like this: I study a hyp and feel, “I’m not entirely sure, but it seems true.” Later, I forget about this feeling, and eventually, I start thinking of the hypothesis as true, almost like the gravity.

Therefore, just after thinking about a hyp, you should write down your confidence and parts you are not sure about. Also, you should to remember this bias to notice it, when you use a hypothesis you thought a lot of time ago.

TL;DR: memory is bad, writing is good, try to do better.