I think this is a very important point for all pitchers to understand. You just have to make the best pitch you can every pitch and then what happens will happen. The pitcher has a critical role to play, but it takes a team to win.
There has been a lot of talk with DD this year about once the ball leaves her hand it's up to the softball gods from there. She's not some all-star pitcher, but she's good and typically initiates soft contact. Our defense was not great this year and even routine things were hard. About half way in she started to get frustrated. So I started repeating the aforementioned line to help her understand she can only worry about what she can control. From there it's out of her hands and she has to move on to the next pitch. Easier said than done.