The planning fallacy is a psychological phenomenon where individuals tend to underestimate the time required to complete tasks and projects, often due to optimism bias and a lack of consideration for past experience or historical data. This can lead to inaccurate estimates, which can have severe consequences in professional settings, such as underestimated project timelines, inadequate budgets, and disappointed stakeholders. To overcome the planning fallacy, individuals can use estimation techniques like using historical data, having someone else estimate, estimating in ranges or building in time for delays, using three-point estimations, calculating a fudge ratio, and estimating during the low point of their day. By understanding the planning fallacy and taking steps to avoid its pitfalls, individuals can create more realistic estimates and improve their time management skills.