If I could only pass on one word of advice, it would be the word “doubt”. If I were allowed two words: “Doubt everything”.
Doubt is the fundamental on which perpetual stagnation is avoided. The moment you become entirely certain of something is the moment you conclude there is no need to review that thought ever again. Consequently, it is also the moment that any mistakes you make become permanent. Conversely, if you doubt everything, then you are almost guaranteed to make progress eventually, as your doubt will motivate you to ask questions and review your knowledge.
When I say doubt, I make no reference to the degree of doubt. I only advise that the doubt should never be entirely gone. I do not expect you to suffer extreme anxiety wondering whether anyone you meet is real, but you should not entirely eliminate the possibility that everyone could be a hallucination. There is a difference between making practical assumptions and scheduling review around your obligations, and forgetting that those assumptions are actually assumptions. Keep track of your assumptions and which beliefs are contingent upon others.
Being entirely certain about anything is, in my opinion, supreme arrogance. To conclude anything with absolute certainty is to believe that you are absolutely incapable of making mistakes.
The only thing I am willing to consider as a certainty is that certainty is otherwise impossible. There is no way for me to know for certain that any feeling of certainty I have is not brought about by some kind of mental flaw.
Consider if you were lucky enough to have an infallible mind. How would you know that you are infallible? You can’t simple know you are infallible because of your infallibility: A fallible but deluded person could also believe they are infallible, it would look the same internally, so your belief tells you nothing even if you’re infallible. I suppose if you had the time and capability, you could test every single belief you have and see if every prediction you could possibly make is true. Even if you accomplish this highly impractical task, how can you be sure that you didn’t misremember the result of one of your tests, or experience a hallucination?
Let me repeat: Even an infallible entity has no way of determining whether they are infallible.
Of course, I could be wrong about this, but if I’m wrong then at worst I’m losing time reviewing things. If I’m correct, and I stop doubting, then I may permanently limit my knowledge. I think something everyone should be careful of is the possibility that their behaviour may enter an inescapable loop. A dead end where they are limited by their assumptions. I don’t want to accidentally spend my life crippled by a mistake in my fundamental beliefs. I don’t want to waste my whole existence walking in the wrong direction because I never questioned the accuracy of the signposts.
Doubt can cause some people anxiety. Just remember that you cannot reasonably be held accountable for genuine ignorance. Just do what you can. You are however at fault if you actively choose to stop thinking. I must apologise if my post has given you additional responsibilities, yet I must also admit that I could not have chosen to allow for any blissful ignorance to remain.
Armed with this fundamental principle, I wish you luck.