What you see is all there is.
Coined by Daniel Kahneman. Even though we like to think of ourselves as rational and objective human beings when making decision. The truth is that we are very well affected by our psychological biases and emotions.
WYSIATI is the bias that leads us to make judgements and conclusions with the information that is available to us. Without considering what other piece of information might be missing. We have the tendency to bend the pieces of the information jigsaw puzzle when some key parts might be missing. Our brain chooses the path of least resistance to form the big picture. It is a machine designed to jump to conclusions.
One way to combat this is to have a structured thinking process and a system to evaluate decisions. Deliberate decision-making can be practiced and it takes time and effort.