Don't start something on a Monday.
I knew this already. You've got enough on your plate having to go back to work after two glorious days away, yet alone trying to make a major change in your routine. Try a random Thursday. Just not a Monday.
I was going to commit to counting my calories this week. It didn't really happen. I did make more of a conscious effort regarding my snacks being mostly fruit and salads for lunch. Did I write everything down? No. (Did I write anything down? No.) Is it okay? Yes.
Cut yourself a damn break. So you had a glass of wine when you didn't really need it. So you had dinner out and got the pasta instead of the broiled chicken. One misstep in your plans, or one day where you eat more than you intended, is not the end of the world and it is not a sentence to a lifetime of failure.
I had a student whose weekly goal was to have a positive attitude for the week. She ended up having a pretty unsuccessful week in that regard, and I was trying to have a chat with her and remind her of her goals on Thursday morning. She says "That went out the effing door on Monday." I asked her if that was any good reason not to try and turn it around at that juncture. While I did not receive a very positive response from her (okay, I got sworn at and a broken pencil thrown at me), it made me realize that all the baggage of my past failures isn't any good reason that I can't keep trying.
No one is going to be perfect at eating. No one is going to be perfect at exercising all the time. Pick a goal that feels comfortable and manageable for you, like eating fruit for every morning snack this week or drinking 2.5L of water every day, and give it a try. Imagine how good it would feel to do it. It may not taste as good as chocolate at the time, but it sure as hell will make you feel better.
What's your mini-goal for the week? Start tomorrow. (Not Monday!)