You need to come up with an asset allocation and stick with it. Maybe that's 100% stocks forever. Maybe you're more comfortable with 80% stocks and 20% bonds, or 60/40. You need to choose a ratio where you can feel comfortable promising yourself that you won't panic and sell everything the next time the market drops (and it will drop, sooner or later). Keep yourself at or near your desired ratio whatever happens in the market. Maybe that means you actually sell some bonds to buy stocks next time the market goes down, as a crash would push your bond percentage way too high. It's a great way to get some stocks when they're on sale!