You will have a really bad headache for a few days due to withdrawal symptoms and will likely be narky and irritable for a few days.
Yep, this started to happen to me after 2 days for about 3-4 days after quitting caffeine because i thought i was drinking far too much. It was surprising and horrible.
Now i only have 2 maybe 3 coffees a day during the week and 1-2 a day at the weekend.
Quitting coffee is for chumps.