How many times since 1897 has the Dow Jones Industrial Average lost 30% or more?

The answer is 11. Basically once every decade and every single time the Dow has went on to new highs. This is part of investing. Deal with it. If you panic during every market down turn you should not be invested in stocks. This is part of the game. Though it can be painful it is a component of the wealth creation process. Nothing that is worthwhile is easy. those who have hung in there have been richly rewarded over time