In principle, there are three ways of knowing about something or someone: what we know, what we don't know, and what we think we know...and it's usually what we think we know that gets us in trouble. When we assume things, we gamble; the bigger the assumption, the bigger the risk.
In any endeavor based on assumptions we can absolutely count on some of them giving way, like support timbers under a house collapsing. Some assumptions may hold for a long time, some almost forever, but most will collapse at a bad time and cause damage. When we make decisions based on facts and when we acknowledge all that we do not know, the long-term outcomes are better.
When analyzing a situation write down what you know, what you don't know, and what you assume. Naming assumptions is key. Want to play it safe? Don't make assumptions. How? Catch yourself making assumptions. - Craig Freshley