1. You might make a mistake in the pedals and panic.
2. You might look down at the pedals and lose your place in the manuals.
3. You might not get the response from the listeners that you wanted.
4. You might start comparing yourself with others.
5. You might have to adjust or change your program due to the organ's current condition.
6. Your registration might be too soft/too loud when the room is full of people.
7. The actual length of your program might be too long/too short in comparison to your calculations.
8. Your music selections might not resonate with your audience.
9, The organ might present a few surprises of its own and you will have to adjust.
10. There's always a risk of messing up registration changes or page turns (even when it's done by the assistant).
Organ playing is an art and art is always risky because it touches and changes people and leaves you vulnerable for the world to touch you back.
There are a hundred things that can go wrong when you perform in public. Instead of wanting to feel secure and safe, it's better to ask yourself "is this the best I can do?"