I've gotten tired of beating my self up when I get off plan with diet or exercise. I have learned to be more forgiving with myself. If I do have an "off" day, I acknowledge the missed day and pick up where I left off instead of quitting. I end up better off in the long run because I get back to it and I feel better reminding myself that I am human!
It is much easier to resume the plan the next day rather than sulk and eat more!