it would be different if you went out in the morning and bought yourself 1 donut, i would say eat it all or only half of it and throw out the other. but you went out because you were feeling depressed and brought home a box. now is the real test, can u just throw them all out? because they will not make you feel any better! i completely understand the whole binging moment, you feel great up until the last bite, then regret sets in. it's ok to indulge here and there, even if their are slight treatment effects. but you made a decision to start eating healthy and exercising! and you can do it if you just keep fighting foward! food is never the answer for life's problems, talk to a family member, a friend, or even a complete stranger of whats bothering you, why u are feeling so sad.
and even if u have already eaten some donuts, don't make urself feel worse, there's always tomorrow.. just dont give up and have the final goal in your mind.
goodluck!