Nervous, stress and anxiousity.
If I stay too long with my own thoughts, I honestly go crazy. Therefore I always try to occupy my mind, as when Im left with my own thougths too long...I can say...I go nuts. That's when my sister jump in and say; Hey wo wo wo, it's time for you to calm down, focus and believe you are strong enough.
She taught me about learning a Mantra. Im sure most people have heard about it but never uses it. A short word, syllable or sound, something you feel you can connect or relate to. Sit down on a floor, legs crossed and arms resting on your legs. Close your eyes and only focus on your mind saying the mantra over and over again. It will leave you with concentration and for the moment everything around you in life is set aside to be handle and picked up when you strong enough and focused after your mantra session.
It's relaxing, try it.