Sincerity Is Overrated
Consider choices like:
Do I push folks at my large company to hire my son?
Do I spend college money from my parents to pursue an acting career?
Do cut open this patient to try my new surgical technique?
Such choices might be justified if, for example,
My son is really good fit for the job opening.
I have an excellent chance to succeed in acting.
This is a very promising surgical technique.
But when am I justified in having such beliefs? Most people think they are justified in acting on a belief if that belief is "sincere." And by "sincere" they mean they are not conscious of just pretending to believe. When they go to the shelf in their mind where that belief is suppose to sit, this is what they find. And they don’t remember anything illicit about how that belief got there.
But sincerity is way too low a standard! Since humans have an enormous tendency toward self-deception, wishful thinking, and so on, we are clearly "sincerely" biased in many ways. So to be justified in acting on a belief, you must have tried to identify and overcome relevant biases. Furthermore, your efforts should be proportionate to the magnitude of the actions being considered, and to the magnitude of the biases that could distort your beliefs. For important actions where biases tend to be large, you must try very hard to consider what you might have seen and felt if the world were other than you think it is.
You will never find a procedural solution to your self-biases. The problem is that no matter how much "more objective" than your initial judgment you try to become, you can never achieve an objective viewpoint. This means that in a way, each judgment is an initial judgment and subject to the same degree of distortion.
Nor is ambivalence/paralysis a refuge, necessarily. Humans tend to regard opposed choices as equal by virtue of being opposed; we're inclined toward dualism. Which is to say, enforced inaction or lopsided compromise are also products of predictable biases.
The only way to be sure you're right about a given question is to be right.
Our biases probably exist to overcome what the first poster discusses: ambivalence and inaction.
Consider a human species that ponders the way you suggest, and then consider another species that acts even if action is reckless on occasion.
Which one will come home from the hunt empty handed more often?
But nevertheless you are correct. While being biased toward doing might be good on a hunt (where most of our evolution in this area took place), there are many many situations where it's very bad in a modern context. Our biases toward wishful thinking, overcommitment, etc. are probably yet another example of something that was adaptive in prehistory but can be very maladaptive in a modern context.