Speaking for myself, the biggest problems in my thinking are as follows:

1. Thinking you know anything with an even remotely high degree of certainty.

2. Confirmation Bias - thinking you are right and searching for evidence to prove you are right, reaffirming your own beliefs in the process and actively ignoring or providing excuses for counter examples and contradictory evidence.

3. Difficulty/Inability of looking only at the facts without interpreting them as you would like them to be or not to be.

3. Inability/Difficulty of admitting you are wrong/made a mistake and also remember it and learn from it.

4. Inability/Difficulty of acknowledging you are an irrational, flawed monkey stumbling around trying to make sense of about a billion things you don't understand and never will understand.

Trying to still make progress given all the above.