bad/badly

Just as you can't feel "good," you can't feel "bad" either. Why not, you ask? Don't you people pay attention? I just told you a couple days ago.

"Bad" is an adjective. If you're describing how you feel, you're modifying a verb. If that's the case, please use the adverb form, "badly."

Therefore, you're feeling "badly," just as you play badly, practice badly, sing badly, and act badly. Come to think of it, you're a mess, aren't you?

However, you can see a bad play, have a bad practice, hear a bad song, and conduct a bad act.

What's wrong with you? You need to just relax for the rest of the day. Tomorrow's another day.