You are not going to eliminate mistakes in manual playing because your hands will still hit the wrong notes from time to time.
Your performance will never be perfect like Bach's because Bach's wasn't perfect either.
You will never be able to please every listener who attends your recital because to please everyone is to not matter to no one.
You will never be able to make every member of the congregation who attends a church service that you play happy because you are not in control of their emotions.
You will never be able to improvise like the world famous masters do because all you can hope for today is to improvise better than yourself yesterday.
So what to do with all these worries that we all have?
When you fear something, sit down on the organ bench and start practicing at least for 15 minutes. Your worries will disappear (at least for now).
Diatonic Sequence in Eb Major: I-IV-V9-I