Many times I’ve seen people dump their stocks when the markets are down.
People think it’s their mistake that they bought stocks & now since they are down, something is wrong with them.
When markets are down, naturally stocks in your portfolio too would be down.
Reverse is also true.
When markets are up & going high, people get greedy & buy at unreasonable valuations (The times they should book profits), some even take leverage so that they don’t miss the rally.
To sum it up, most people buy at high valuations when they should avoid buying & sell at lower levels when they should actually be buying.