We frequently plot our goals onto timelines. But, in doing so, we often succumb to the planning fallacy.

In the book Thinking Fast and Slow, Daniel Kahneman explains that people have a tendency to underestimate how much time is needed to complete a task, like in a home renovation. “When forecasting the outcomes of risky projects…[we] make decisions based on delusional optimism rather than on a rational weighting of gains, losses, and probabilities.” That’s why it is crucial that we attach our goals to realistic timelines. Realistic timelines can be ascertained by comparing our goals with a reference class of past, similar projects.

In Lean In Sheryl Sandberg suggests that we set our goals according to an 18-month timeline. A year is often not enough time. We tend to over-estimate what we can accomplish in a year. But, two years feels too far away.