We talk about this all the time. Some nights you are throwing the ball different all the time but you make one mistake to counteract the other one and the ball hits and carries in spite of all the things you did or didn't do. Then the next night you can have the best looking ball you have thrown in months and leave pins standing all over the place. It's bowling and that just will never change.
Humidity, amount of heat in the building, temperature of the lane machine when used, temp of the stripper when mixed, when the lanes were oiled, who is bowling against or with you, and on and on and on, all plays a role in what happens. How much each of these have to do with carry is debatable, but they all have a bearing on your perception of how you are throwing the ball.
I sometimes wonder if what I consider a "good" shot is actually that much different than one I think isn't as good. You can go by feel off your fingers to let you know when you got a great release, get feedback from the ball path as to whether you have hit the correct area of the lane, and read things into what pins are standing and how they fell, but in the end sometimes it is just plain luck as to whether the pins fall or not. So despite what you think about your execution, score sometimes can be subject to other things. Of course the better your execution, the higher your scores will be in the end (average), but there are those days when score just isn't an indicator of effort or ability. Thankfully that doesn't happen that often.
