It's an average inflation-adjusted expected rate of return over time of a balanced portfolio, not a guaranteed rate every year. Some years might be 10%, some ye

It's an average inflation-adjusted expected rate of return over time of a balanced portfolio, not a guaranteed rate every year. Some years might be 10%, some years might be -10%. Historically, about 4% is the safe drawdown rate. FIRE folks tend to be a little more conservative than that, though, because of the even longer time horizon involved with retiring earlier. Check out a tool like https://www.firecalc.com/ https://www.firecalc.com/ that is designed to run backtested simulations to see if your drawdown rate from your starting assets would historically be safe for your time horizon. The UI is clunky but the math is good.