Don't advertise your resolution to others. That way, you won't feel the added pressure that comes with messing up in front of the whole world. Be your own boss. It's hard enough to change something that you want to change. It's even harder to change something that other people tell you to change.
Failure is part of success.
A big part of sticking to resolutions is getting through bad days. They didn't break their resolution. They just had a bad day. Don't focus on the day when you failed. Focus on all of the days when you won.