TL;DR: I believe I'm stupid because I can't instanly form an opinion on something or because I make logic errors/I have a bad judgement or a flawed belief. Why couldn't I have thought of the correct opinion in the first place? Why I feel like I can't stand by my opinions and I'm so unsure of myself. I always feel like I don't have good arguments.

I'm always dissatisfied with my judgement and reasoning. I feel like I'm never sure of my opinions and everything seems so relative to me. I feel like I could be convinced easily into thinking another way if I notice the arguments are better. And maybe those who state these logical arguments aren't necessarily right but I am so discouraged by their great ability to debate/defend their opinion that I think I could never stand by my opinion so well. So many times I'm not trying because I get discouraged.

How are they so sure of themselves and can form an opinion/impression of something so early? I seem to have to think days on end until I reach a final conclusion for my self.

I obsess over my logic errors and the fact that I hardly realize what another says in a debate.

For example I know in most cases this way of thinking is wrong but I can't get rid of it. It is as if it's part of me:

If a thing works for the majority that means it is the correct thing/the truth. That statement is obviously not true. 400 years back the majority of people thought that burning people on stake for not believing in God was the right thing to do and it is not.

But in some cases I tend to think like that especially if my example wouldn't affect other people like in the example above. However some people told me that I must get rid of this way of thinking regardless because it's counterproductive to evolution.

And I feel very bad about myself because I wasn't the first one to think of it or that I was slow in understanding this concept.

I many times find myself after a long time realising the people I debated a subject with were right.

I feel so doubtful, unsure of myself. I believe that I am very stupid...