A grudge can feel useful.

It can feel like a shield. Someone hurt you, betrayed you, embarrassed you, ignored you, abused their power, broke your trust, or left you carrying the cost of their choices. So you pick up the grudge and hold it close. It reminds you not to be naive. It helps you remember what happened. It gives you a sense of control when something is taken from you.

And if we are honest, a grudge can also feel strangely satisfying.