Dizziness, anxiety, insomnia, headaches, can't deal with light, generally full of unpleasant mental feelings, maybe you'll get some non-headache pains, and some people seem to get straight up dysphoria but this seems very rare.
If you were taking it consistently for a medical issue, you might get rebound symptoms related to that particular issue (like if you took it for seizures, you're maybe gonna deal with seizures in withdrawal; if you took it for nerve pain, you're gonna have bad nerve pain; restless legs, that's gonna be back with a vengeance).