Humans were created with passions. You can't be a human very well without them. And yes, the way Thomas Aquinas uses the word "passions" translates more accurately to our broader word of emotions, or even appetites—those feelings we undergo. But for the sake of this homily, it actually probably works to let more of the modern sense be heard too: that which drives us, what has a hold on our minds and hearts.
Anyway, Aquinas divides the eleven passions/emotions in two main groups: the "irascible passions" (hope, despair, courage, fear, anger) which I messily described here as the fighty or pugnacious passions, and the "concupiscible passions" (love, desire, delight, hate, aversion, sorrow) which I've heard described as the "simple" passions, but for this I prefer the descriptor of the desirous passions, or the attractive passions. Those that are about what is pleasing, enjoyable, beautiful, and that which makes us feel content.
And the passions are not bad things. At worst, they are morally neutrally. At best, they drive us to work for important things. And people tend to have one or the other that leads them more: Is your first thought to revel in the good, the true, the beautiful? To want to marinate in the and find comfort in the gifts and works of both God and man? That's the desirous or attractive passions. Is your first thought to work, defend —even fight— for justice, for the unprotected, for that same good, true, and beautiful? That's the irascible or "fighty" passions.
In the homily (pulling from the gospel) I ascribe the expression of "thinking with your stomach" to the desirous passions and "thinking with your fists" to the irascible passions. And hopefully I made clear that those realities of personal, mental alignment aren't bad. They just are the two ways we tend to talk ourselves into not listening to Jesus when he has hard lessons for us to hear.