Jumping into a dark hole with only a guess of how deep it is, that's scary.
But that's what our job requires. We need to make decisions with limited information, and all we have is a blurry outline.
Reid Hoffman has an approach called provisional decision-making. He makes a decision based on current information. Then he'll decide what information he needs to disprove his decision and get it.
There are lots of tools and frameworks for making decisions. What approaches have you found work for you?