My grandpa watched me struggle with a stuck faucet for 15 mins then said "you're fighting it instead of working with it" | Fix It Yourself - Guest Forum
And honestly your grandpa was right on the money, I had the same exact thing happen with a rusty pipe under my kitchen sink last month. Sometimes we just muscle through stuff out of frustration instead of taking a breath and feeling where the problem actually is. Next time try a little penetrating oil and steady even pressure instead of brute force, it really does make all the difference.