Knowing what you're going to do before you do it is huge. If you can remove a bit of uncertainty, it allows you to loosen up and your reflexes and focus are more on point. Basically, know your strategy for that machine before going in, and rehearse in your mind the shots you need and want to hit. Visualize hitting those shots.
That said, have a backup plan. If the machine is unfriendly to that first strategy (a backhand shot isn't working, you're just struggling to find a specific shot, etc.) be able to quickly transition into a different plan without just letting your mind go into that chaotic, "WHAT DO I DO NOW?!" state. The more you can lean on reflex and that flowing feeling rather than thinking stuff out on the fly, the better I find the shots to go.
I also agree with feeling good physically. Comfortable shoes and clothes, being rested, and a mind free of too many distractions all help. I listen to music when I compete, as it helps me block out anything going on outside of the little bubble that I and the machine exist in.