"I'm glad I got that decision out of the way, now I'm going to get some donuts for breakfast. I might as well enjoy my guilty foods now since I'll be dieting soon."
My advice, if you want to lose weight, do it now.
Eat in a healthy manner now.
There is no moment as powerful as right now.
If you absolutely can not get out from behind a desk right now, make now as soon as possible. You don't have to go and run 5 miles on your lunch break, but you can take a 10 minute walk. You don't have to switch to nothing but grapefruit and salad, but you can pass up fast food for a healthier choice.
Make some small changes to your life. If you eat lousy food from a fast food joint for lunch every day commit to only doing it twice a week and start preparing healthier food to throw in a lunch box. Make sandwiches for lunch or make enough food at supper to have leftovers the next day.
If you don't exercise at all. Do something.
Add a 30 minute walk to your day 5 days a week. If that seems like too much time, think of it as an investment, you will get the time back with a longer lifespan, not to mention it will reduce stress.
Do 10 pushups in the morning or before bed. If you can't do a pushup, start with wall pushups.
Don't wait until after Halloween/Thanksgiving/Christmas, change small things now.
If you just can't resist Thanksgiving dinner, splurge a little that day, one day is small stuff when you are making small changes in your daily life.
Make some small changes to your diet and your activity level NOW.
Next month, do it again.
Lather, rinse, repeat.