Pump and let go
Before the very important "performance":
1) Pump up your body (by doing intense exercising). Put a psychological pressure on yourself (think how important it is to succeed in it)
2) And then let go. Use this energy for having energy and freedom in the performance. Fuck it, allow mistakes.
Buddha said: Attachment to results is a cause of all suffering. Before the "performance" day do everything very slow. Don't rush it. Sleep very well (try 8-10 hours)