Why can't I know it all as a new nurse?

I am frustrated after today. While working today (not as a nurse or even in a medical faculty) a customer had a TIA. His family said it happened recently and they knew what wa going on. I was trying to see if the customer would respond to me, but he didn't. He could not squeeze my hands, pupils looked equal and round. He was sitting upright. He had several layers on and was sweating. I unbuttoned his shirts. He started to slouch down And another nurse came over to hold his head up while we waited for an ambulance. By the time it got there he was responsive, knew where he was and able to squeeze hands.I am mad at myself because I don't know if I could have or should have done more. I wasn't nervous. I was very calm. Just seeing this other nurse jump into action who has 30 years to my 0 experience, made me feel so foolish. I know I have so much to still learn.Sorry for the venting.