It gets better surprisingly quick, at least for me. Get to day 5 you will probably notice a difference. I think a lot of people (myself included) go for years not getting past day 2-3 and that makes quitting much more intimidating because you have a distorted view of how hard it is.
The best thing I've learned when approaching quitting from day 1 is to accept insomnia. Not sit there in the dark with my eyes wide open trying to force sleep. I'd rather just keep my mind occupied--it wants to go a mile a minute so just let it--and though it makes for a tired first few days it's less stressful than tossing and turning.