Find your zone, try to get into it and have faith. I try to do this: Do not dwell on partner's absence; instead, view it as an opportunity to get into your zone without distraction. Your decisions are now simplified and are just yours, not a coordination. You can break down your tournament into manageable chunks and focus on only the next fish, one spot, and one hour at a time. Try to make sure your internal dialogue is positive? For example, if you say, "I am at a disadvantage fishing alone," change that to, "I can adapt more quickly without coordinating decisions." Keep your energy up, hydrate, eat, and maintain focus. As BLat says, know what you are good at and your confidence baits, then find those fish. It is essential to have faith and visualize yourself handling the tournament well and managing the situations effectively. 

Take your time , setup your equipment to land fishy and relax while fishing. You can concentrate on boat positioning without any concerns of the backseat angler. Except the challenge as an opportunity.

I talk more to myself to keep my confidence up when no one is around and this way nobody knows. 😀