Mistakes are inevitable in the world of entrepreneurship. The challenge is to turn them to your advantage.
CONTROL YOUR PANIC RESPONSE. Calm your pulse with deep breathing rather than a dose of caffeine.
ELIMINATE SELF-PUTDOWNS - they won't help you think rationally. Instead, calmly re-state the facts (eg, this is only my first mistake of the day/week/month).
WRITE A LIST - about anything. Even noting all the rectangular objects in the room forces the brain to think logically.
IDENTIFY WHAT YOU HAVE LEARNT. Swallow your pride and discuss the mistake with a more senior colleague