It could be a tricky spot with that long double pedal trill in the pedal part (like in Liszt's B-A-C-H). For a lot people it may even be as "simple" as putting hands and feet together in the chorale preludes from Bach's Orgelbuchlein. Even playing left hand part and pedals combined in many cases where different rhythms are employed might be a very complex task.
If you are an organ improvisor, things can go out of control very quickly - having no interesting ideas to play on, having interesting ideas but limited technique may lead to frustration.
If you compose for the organ, a search for originality might be a daunting task. Or we think we wrote something clever, but it sounds dry and unmusical.
So we get stuck. What to do then? Should we quit and do something else? Should we continue the task no matter what?
These are hard questions to answer. I think, you can try to imagine the end result. If the end result doesn't feel exciting enough, perhaps it isn't worth pursuing. The really remarkable things are supposed to be difficult.
Sometimes it means that you have to find easier piece and come back to the difficult one when you are ready for it. Sometimes it also means you have to push yourself one step further and stick to the plan.
But the most difficult thing in such situation is to face ourselves strictly and honestly. Remember, it's not really the music we are struggling with, it's we and our weaknesses.
Our biggest opponent is ourselves.
By the way, do you want to learn my special powerful techniques which help me to master any piece of organ music up to 10 times faster? If so, download my video Organ Practice Guide.