I'd say one of the most common mistakes an investor makes (among many however) is the fact they really don't build their portfolio around a specific investment style or risk tolerance.
Then, when something like what we've witnessed the last few weeks happens, they're exposed to significantly more volatility than they can handle. In the end, they can end up selling strong stocks at discounted prices due to nothing but panic.
The issue is that most all investors think they are high risk in a bull market, especially when they're new. Everyone in 2020 who was new to the markets thought they were "high risk" because it had been green for a year. Fast forward to that correction, and some put themselves in a horrible position mentally, and some may have made mistakes.
If you have a $100,000 portfolio, how comfortable would you be if it went to $60,000 in a month? $80,000 in a month? These are things you have to factor in, and most people don't.
The easiest way to solve it in my opinion? Err on the side of caution and start off more conservative, branching out to develop a higher overall risk if you're comfortable with it.