I don't think I'm following, you didn't "lose" anything if you didn't sell. Even if you invested in 2007 at the peak and lost 50% of a 100% S&P500 portfolio by

I don't think I'm following, you didn't "lose" anything if you didn't sell. Even if you invested in 2007 at the peak and lost 50% of a 100% S&P500 portfolio by 2009, by now you'd be extremely wealthy, adjusting for inflation. A $10k investment in 2007 is now worth $27k and that assumes you didn't contribute another penny for 16 years.