Here are few things not too many people know until they actually have money invested.
Not every trade goes to plan- just because you plan on making money and you take a trade doesn't mean you will be profitable. KEEP YOUR HEAD UP there are many more trades to comes.
Being in the red doesn't mean you are staying in the red - Just because you may take a red trade early in the day doesn't mean there are not potential trades you can take to get back in the green, the key is not overtrading trying to chase a number
Trade with what you can afford to lose only- If you can only trade with what you can afford to lose the emotions can be sidelined and focus on the objective which is trading consistently
Taxes - Make sure you understand how taxes work with gains so you can put money aside and prepare for them so you don't have a big surprise at the end of the year
Its not easy - Nothing worth having comes easy. The key between the people who are successful in the stock market and struggle is consistency.