We believe we make logical, conscious choices. In reality, we are quietly guided by our subconscious minds full of biases and misconceptions.
Cognitive biases mess up our view of reality and tweak it without us knowing about it. All you can do is educate yourself and then keep a watchful eye on when they pop up. You will still miss many of them, but you may catch your brain playing a trick on you every now and then, and you may fight back.