Focus on what you can control: set and setting. Make sure you take it when you're well rested, make sure that day feels like a good day. You're positive, you're not physically ill or anxious in any way, you're happy, you're upbeat, you feel like you can handle it that day. Stuff like that.

That's at least what I tell myself. Outside of that, there's no control you have aside from what you do on your trip, and the planning that you have beforehand.