gut feeling

go with one's gut

To trust or follow an intuition or instinct, as opposed to an opinion based on a logical analysis.

gut check

An honest, reflective appraisal of one's true feelings concerning a matter of concern.

gut factor

The emotional dimension of decision-making. A person's subjective (often almost visceral) feelings about what is right or wrong, good or bad.

gut out

To endure stoically.

gut reaction

A visceral reaction that arises with little accompanying thought or even (sometimes) no thought.