Here are some of my favorite mental models (quotes are from Shane Parrish's Farnam Street blog)

Inversion

"Inversion is a powerful tool to improve your thinking because it helps you identify and remove obstacles to success. The root of inversion is “invert,” which means to upend or turn upside down. As a thinking tool it means approaching a situation from the opposite end of the natural starting point. Most of us tend to think one way about a problem: forward. Inversion allows us to flip the problem around and think backward. Sometimes it’s good to start at the beginning, but it can be more useful to start at the end."

Pre-mortem

Unlike inversion, which starts with the desired end in mind... a pre-mortem starts by asking, "what is the absolute worst-case scenario?" and then works backward from that scenario into the event and milestones that would need to occur for the worst-case future to actualize. Knowing what these milestones are is the first step in actively avoiding them.

Incentives

"All creatures respond to incentives to keep themselves alive. This is the basic insight of biology. Constant incentives will tend to cause a biological entity to have constant behavior, to an extent. Humans are included and are particularly great examples of the incentive-driven nature of biology; however, humans are complicated in that their incentives can be hidden or intangible. The rule of life is to repeat what works and has been rewarded."