Are you nervous you won't be able to prepare adequately for your public organ performance?
Chances are you are not giving yourself plenty of time to prepare.
You see, even though you can master 4 measures a day, 1 page a week, 4 pages a month, it doesn't mean you will be able to perform a piece which is 4 pages long after one month (unless you're an expert in which case it's completely different story).
My rule of thumb is to play a run-through of your organ recital at least 30 days in advance.
If you learn at this pace, you can only play the piece without stopping after this month with lots of mistakes.
So add one more month to this piece and then you can feel how the performance anxiety gradually diminishes.
Plan well ahead.