fire in one's belly

/F AY1 ER0 IH0 N W AH0 N EH0 S B EH0 L IY0/
noun
  1. 1

    The emotional stamina and vigor, passion, or inner drive to achieve something, to take action, etc.

Source: https://en.wiktionary.org/wiki/fire%20in%20one's%20belly, https://en.wiktionary.org/wiki/fire%20in%20the%20belly