We have all had bad days where we overeat or miss our exercise goal. It can be very discouraging. You need to dust yourself off and get back up. Lick your wounds and get back out there. Success at anything you do is just repeated effort. I try to avoid the word failure and focus on the term less successful endeavor. You will get there, so keep trying.
Success is the sum of small efforts, repeated day after day.
I like to say weight loss and being healthy are like running a computer program. You need to get the program started and then keep hitting run every day to continue the progress.
Successful weight loss takes programming, not willpower- Phil McGraw