Thinking in terms of the variability of outcomes rather than in discrete terms.
News Flash: Predicting the future is tough. When you are developing time estimates, goals, cost and revenue projections or other numerical predictions, use probability. So instead of committing to a single outcome, like we will finish this game in 3 years, take a page from stats and use probability: There is a 90% chance we will complete this game between 2 and 5 years. Thinking like this helps you identify risk and encourages mitigation strategies.
If you want to make probabilistic prediction you’ll need some basic statistics knowledge. I suggest brushing up on normal probability and confidence intervals. The book “How to Measure Anything,” also has a lot of good info on how to think in probabilities.