By definition, we cannot know everything there is to know, about anything. We can know something's velocity, but not it's location. We can know it's location, but not its velocity.
Eventually, we have to take what we know and assume we know enough about it to make an “educated” decision, and move forward.
Granted, one person's “educated enough” is another's “barely above ignorant”, and yet another's “over-thought it to death”.
This is the beauty, and the terror, known as “giving it one's best shot”.
It comes down to a balance over over-coming laziness, and not missing the boat.