Not easy for me to talk bout this but, to let you understand, I have to set some background first.
I have a chronic disease. Years ago I really suffered from it, but after the adequate treatment was found, my health improved and I gained some (relative) peace of mind. Anyway, from a literary point a view, I felt that I had to write something on this subject. It was an evidence for me, and it came all naturally. The result was a short story (but, somehow, I knew that It could have been more than just a short story.)
End of the background.
I'm presently writing a novel. I have worked on it for a long period, and I can say (after many difficulties) that I'm enjoying it now.
But lately, after years of a steady state, I'm living again a rash of this disease. And once again, I'm feeling this need to write all this ***** down, but here is the dilemma.
On the one hand, I don't want to abandon my novel, invented, patiently assembled, and wich represents a long work.
On the other hand, there's something more urgent, more direct, more spontaneous in the other work (not really yet a novel) something inner to me, something that comes from my guts.
Sorry, things are going a bit wrong for me, I'm just confused.
You can plan your time to write both. Continue with your novel considering that you have invested much time and effort writing it out. Spend some time on it to get it completed. If you are not in a hurry to get it publish, it should not pose any problem at all as there is no deadline for you to meet.
If you are writing it because you are full-fledged writer and your publisher needs your novel immediately, then you'll have to prioritise.
As for wanting to write something based on your gut feeling, well...you can always draft it out whenever you have time to spare.
If you plan your time well, I guess you'll have no problem tackling both. What is important is that you write at your own pace, that is if you're writing it as a hobby.
Oops, your inner-voice.
Find a quiet moment to lie down and relax before you go to bed. Think about what's troubling you. Then listen to my inner-voice. You may find that you wake up with the solution to your problem.
I hope that helps.
Good luck.