Instead of feeling down, use it as motivation. Keep that picture by your side and look at it any time you are craving the wrong foods or don't want to workout. Tell yourself how you felt at this moment when you first saw and that you don't ever want to go back.
If you are going to win any battle you have to do one thing. You have to make the mind run the body. Never let the body tell the mind what to do. The body will always give up. It is always tired in the morning, noon, and night. But the body is never tired if the mind is not tired.-George W Patton