Look ahead, not behind. This phrase applies to more than one area of golf.
First of all it’s very important in maintaining a good pace of play. The location of the group behind you is not important. The location of the group ahead of you is. You should be within a shot or two of the group ahead or YOU are playing too slowly.
Secondly, you can’t do anything about the shot you just made. The only shot that’s important is the shot you are about to make. Put the best possible swing on each shot and after that, what happens happens. Move on and look ahead. As a friend of mine told me, “Pick up your bag and walk to your ball.” That’s all you can do.