I'm going to miss, I'm going to miss, I'm going to miss, then you actually miss, How do I fix this?
Usual disclaimer, I am not a certified instructor....
My question is: Why would thinking about missing be your first instinct?
If you've played a reasonable amount of time, you probably have a catalogue of shots in your head that you consider "easy". In a way, these are "confidence builders", where you may take them for granted but still complete them. Over time, this catalogue can grow, so that what you consider easy/makeable puts more shots well into your confidence zone, so that you think less of missing and more about the results of your execution being what you expect--to make, as opposed to miss.
You can also change your negative mantra to a positive one, but I would instead suggest adding some mental steps to your PSR. For example, when sighting up a shot, ask yourself, "Is this shot makeable?", and if/when the answer is "YES", then the follow-up is, "How do I make it?" The second question should lead to the usual, aiming/alignment process for shooting, and then that should be where your focus goes--executing the plan (of how to make the shot successful).
Also important--REMEMBER TO BREATHE.