Is using chantix difficult or is it just the nicotine withdrawal?

Probably both: Nicotine withdrawal symptoms can be diminished by using nicotine replacement drugs (gum, patch, inhaler, nasal spray) and/or bupropion and varenicline ("chantix"). Varenicline ("chantix") is an effective helper, reducing both cravings and the reward of using nicotine. It can cause strange dreams, but nicotine withdrawal can also cause irritability, poor sleep, and increased appetite.