Ideally you set yourself up with an Investment Policy Statement which includes your ideal asset allocation (based in risk tolerance and goal-setting), as well a

Ideally you set yourself up with an Investment Policy Statement which includes your ideal asset allocation (based in risk tolerance and goal-setting), as well as rules for rebalancing, such as 5% drift outside that asset allocation you want. So if equities are down 20% but bonds are stable (or better!) you end up selling bonds high and buying equities while they are cheaper. If you didn't plan ahead, you shouldn't be making plans now. If you have cash or other assets with less growth potential, it may be a good idea to sell some to buy equities. But before you do that, zoom out and look at 5 years of index fund prices. This 20% correction reaches back to about December 2018. But has not appreciably negated the growth between 2009 and then!