I go through a little depression every time I start a diet. It's hard. It could be chemical (like a withdrawal from sugar, caffeine, or other 'substances' you are used to) or it could be psychological. If you are an emotional eater and turn to food for comfort, of COURSE you are going to feel down if that "friend" is no longer there to make you feel better. Give yourself a break, because it makes sense that you are feeling this way.
The sooner you discover something to replace that old friend, though, the better. When you are feeling down, instead of turning to food you've got to almost FORCE yourself to turn to something else. It could be exercise, reading, dancing, or talk with a good (human) friend. Just a bunch of different things until you find a few options that work for you. For me, distraction is key... so going to a movie is great, or just hoping in the car and going to the mall for window shopping works too. If none of those things seem to help, and you've just gotta get something in your mouth... try a healthy lo-cal food like one of these guys -->
I know from past experience that this is such a crucial time. You are really at a crossroads. You can either go on one path that leads back to old habits for comfort, or you can choose to go down the other path that leads to newer, healthier habits. Of course, one road is easy to take in the short term, but you know how that road ends.
The other road is tougher, but it leads you to a much much better place. If you can work through this day, and then the next and the next, before you know it you will be learning new coping mechanisms and be on the other side of the "withdrawal" stage of any physical additions causing these feelings.
You can do this. Just take it one day at a time. One minute at a time, when necessary.
I don't know if any of this helped... but I mostly wanted to tell you how much I can relate to where you are at right now, and give you a big hug!