If you are

When your mood changes so much, you learn the right thing to do. The action that yields the best results. I have experience to back me up, but don't just rely on my advice. :)

If you're happy, believe in it! Speak with conviction and have faith in yourself.

If you're angry, doubt yourself. Be cautious and wary about this passing emotion.

If you're truly sad, cry.

 

If you're overwhelmed, write.