This is my number one regret
It was years later when I actually had some money to invest
The stock recently had a very large drop and I felt like it was around its bottom so I set a buy order for 60 shares at $180 pre split ($36 post split) when it was at $182 a share. it never hit $180 and because of that $120 ($2 x 60 shares) mistake I missed out on the order which would now be worth 300k