I know it's hard, but concentrate on the big picture. Ask yourself what else you could have done: nothing. You stayed on your food plan and exercised. You will never be perfect because a little thing like life gets in the way sometimes. Just concentrate on the goal and believe that if you just follow what has been working you will reach it. It's better than the alternative no matter what.
"There is no use trying,"said Alice; "One can't believe impossible things." "I dare say you haven't had much practice," said the Queen. "When I was your age, I always did it for half an hour a day. Why, sometimes I've believed as many as six impossible things before breakfast."