I'm sure general sports psychology could be applied to RC to improve performance, mentally. Good diet and general fitness should also help the physical side.
Personally, I always make sure the car and equipment is prepared before I arrive at the track. This means I don't have to start the meeting in a rush to get the car ready, and also means I can be relaxed and know that the car will work when I put it on the track.
Before a race, I may spend a moment going around the track mentally from my position on the rostrum. Visualisation.
I don't really have any "conscious" thoughts while driving. I've been doing it for quite a while now so I can "read" the track and my competitors, using my peripheral vision to keep a few corners ahead of where I am, and to see the gaps between myself and my competitors. My main focus is on being focussed on the driving.
A close race is good, it builds up a bit of adrenaline that speeds you up. Getting stressed with too much adrenaline tends to make me go to pieces, and I start over-driving and slowing myself down.
Distractions on track and on the rostrum can ruin your focus too - e.g. a marshal blocking your view, or someone one the rostrum taking the banter a bit too far.
So I suppose my first bit of advice is be prepared. My second piece of advice is stay focussed. My third piece of advice is to use adrenaline to your advantage. Then the results should come.