Through a glass darkly
Some people will immediately recognize the reference in the title; others will have no idea. This is partly true because the quote is from the bible, and partly because the quote is metaphorical.
Whatever your beliefs about the bible, it is worth considering the phrase "Now we see as through a glass darkly. . . " You can imagine looking through the side of a pop bottle if you like. Now we see as though there were a piece of dark, heavy glass between us and the situation we are observing. Whatever we see, we miss the details.
This is a fairly accurate description of what happens when we look at ourselves. Even when we stand under a bright light in front of a mirror, what we see is filtered through how we feel. It's true when you ask "how do I look in this outfit?" and it's true when you ask "how will I succeed in this new job?" Self-reflection is never 20/20. It's more like looking through a glass darkly.
This means that we never really make decisions the way we say we make decisions. Our ability to see our own process is coloured and distorted by what we think we should believe, by our previous experience, by our hopes and fears. We don't know what we are doing while we make the choice, much less how the choice will affect us after it is made. Whether we choose by guessing or by analyzing, we are not good at knowing what to choose because we are not good at knowing ourselves.
How can we get better at choosing if even the people who study our choices are looking through a glass darkly? The routes to a better process begin with recognizing that the one you are using now could be better. The world is full of people who looked through the glass darkly and made a good choice anyway. The question is not how they got better information; it's how they did their best with the information they had.