Very interesting question. I think it may have a lot to do with the individual. Different people are motivated in different ways. There is a lot to be said for being able to focus intently on the task at hand and that has a lot to do with how you are able to fade the distractions, mental and physical. I think both of those types of distractions can be mitigated by being relaxed and centered. I shoot my best when I am relaxed, but there also has to be a will to win. I find I will sometimes back off on a player when I get a lead or feel I'm getting too many lucky rolls. It's not really a conscious decision that I make but more of a further relaxation brought on by less desire to focus as much on winning. When playing someone that I really want to beat, I will keep my focus up at a very intense level until the match is over.
Last night while practicing by myself, I fell into a place I've never really been before (for very long, anyway) where I felt so in tune with the game that everything became very easy. In this instance, there was no real drive to win or beat someone, just a feeling of extreme confidence and total relaxation. There's also a strong feeling of enjoyment.
I have played very well when I've been angry before, but I don't think that's sustainable over time. Unless you're wound up like a top, it's hard to be angry at every opponent you meet as well as sustain the anger over the length of a match or tournament. I think eventually you would lose whatever advantage it gave you due to the distraction. Ego is a good motivator, too. You don't have to be outwardly egotistical to use your ego to motivate. Ego is what got me back into this game so heavily. I got beat by a couple of people that I knew if I was playing as well as I used to, would have no chance. It only took a couple of months of practice to get to that level. I'm way past that now and have other motives for continuing. We all feel good when we play well and the crowd/team is cheering and giving us atta boys. That's just ego stroking.
I feel that cool, calm, confident, relaxed, and focused are the main ingredients for a good player. A little desire will help sharpen the focus. All the rest are distractions to be avoided unless you can use one temporarily to bring you back from a state of apathy. Enjoying what you are doing just makes it that much easier.