Stress
Your level of success rises and falls with the performance of the stocks you buy and sell, so you'll likely be in a continual state of feeling like the gambler praying that the little white ball lands on "red." The only difference is that you have some influence in the matter. Which can make it even more stressful is that if your stocks fail, you fail. You may want to consider having that tattooed somewhere on your body as a reminder.