What a cool term..the Gut-Brain Axis. It was coined by researchers who have found a strong link between good bacteria in our digestive tracts and our feelings and thinking ability.
NPR had a good piece on the topic this morning...here's the link:
This is why we often talk about "going with our gut" or "that was a gut check" or "she made a gutsy move" or "I have butterflies in my stomach". Our vocabulary describes what we instinctively knew but now seems proven scientifically.
Trust your gut as you persevere.