Trading is an amazing endeavor. It involves an huge emotional component that I didn't expected when I first begun and I think many traders can relate to this.

Emotions run high when you are about to get in, when you are in and when you are out of a trade.
Greed. Fear. Hope. Euphoria. Sadness. Regret. . All of those can be felt in the course of a single trade.

Sometimes you will hit a really bad trade that makes you feel like an idiot, or you will go through a losing streak that will make you question yourself if you are really going to succeed at trading. That kind of event can really affect your emotional state and in turn, affect your trading even more.

In those cases, I like to remember that I must believe in myself! 
I must remember that succeeding at trading is possible, it has been done.
I must remember that most successful traders had a hard time their first months or even years; they burned several accounts become they became consistently profitable.
I remember that I must keep going.
I must learn from my mistakes;
I must review what is working for me and what not.
I must focus on what I'm doing right and avoid what I've done wrong.

I must believe in my strategy.
I must believe in my skills.
I will believe in myself.