Common trading mistakes include blindly following trends, buying and selling without analysis, which easily leads to the trap of chasing highs and cutting losses; excessive trading, where frequent operations increase costs and decision-making is prone to emotional impulses; ignoring stop losses, unwilling to admit losses, causing continual expansion of losses; trading against the trend, attempting to catch the bottom and top while going against the overall trend; and lacking a trading plan, with unclear goals and strategies, leading to random buying and selling. These mistakes are often caused by unstable investor psychology and insufficient preparation, which can easily result in capital losses.