I struggle with this. I still get a rush of adrenaline when that first game starts and it affects my shot. I struggle to try to keep my mind off the score and just execute but it is difficult. I am also guilty of figuring out what I will have if I strike out but only on bad games where I am trying to salvage a decent game out of a mess. I do not do it in good games.
First off Scott and Tuba, like I said earlier, take about 3 or 4 shots near the end of practice to really gun the ball down the lane. That way all that pent up energy and anxiety (and adrenaline) can be released and you're good to go.
As for the score, I only look at the scoreboards for two reasons. the first is to see how much handicap my team has to make up. The second is to help with my own seperate score sheet that I record all of my data for later on. Otherwise, I'm more focused on how the lanes are changing and how I need to adjust to them.
You should never contemplate your scores and especially your missed shots or spares. I have teammate that does this on a consistant basis. And while it is good to make a note of it so that you can adjust, it is not beneficial at all to obsess (that word might be a little too strong but whatever) over a missed shot or a shot that you thought was going to put all ten in the pit and didn't. My teammate does this a lot and it hurts his game very bad sometimes.