That really depends on what you trade and how you trade it. If you invest in S&P 500 ETFs, you could lose a significant chunk of your investment during a recession, but you'll never lose everything. Diversify and you will have that same comfort. If you are willing to hold long enough, you'll make back your losses.
Just look at the Dow Jones, it peaked over 14,000, dropped to 7200 and here we are back at 12,000. As long as the world economy continues to grow, so will these indexes.
If you want to get rich, you'll need to take risks, it's no different than owning your own business.