Why is the timing of a market crash more dangerous in my first retirement years than later on?

This is the heart of sequence-of-returns risk. When you are still contributing, a crash early on is actually helpful because you buy cheap shares. But once you are withdrawing, a crash in your first few years forces you to sell more shares to fund the same spending, permanently shrinking the base that must recover. Two retirees with the identical average return over 30 years can end up with wildly different outcomes purely based on whether the bad years came first or last. Poor early returns combined with steady withdrawals can push a portfolio into a hole it never climbs out of, even if markets later boom. That is why the first five to ten years of an early retirement deserve extra caution through cash buffers, flexible spending, and a slightly lower initial withdrawal rate.