The most important thing is to expect the ball to go in the hole. That is where it belongs. Keeping your body still, create a clockwork rhythm in your putting action. If you keep it as simple as counting one-two-three, you will create an ability to putt with the timing of a metronome and you can expect to sink more and more balls.
If you expect to miss you will. If you expect to achieve the putt you may well do so. Champions expect to make every putting attempt and just because they miss some, it doesn't affect their belief in making the next one.