you have to break the cycle of instant gratification. just because you want a donut doesn't mean you have to have the donut now. if you don't eat the donut in front of you, it's hardly going to be your last opportunity to have a donut. it's getting the now off the end of i want it. the general idea works for curbing spending too.
you can do this several ways.
1. overeat. when you realize you've already gone overboard simply because something was nearby, grab a few more. focus on how full your stomach feels as you eat one more that you didn't really want in the first place, then a few more. if it's something that is shelf stable and has a decent amount of fat, pay attention the waxy taste that comes along with several servings of the food. if it's sugary and you start to sugar crash, pay attention to how you feel as you are crashing and make sure you focus on it to remember as part of the experience. focus on how full and uncomfortable your stomach gets so that the next time you pass that temptation you have a rather unpleasant range of how you felt the last time you had it. it's a little easier to skip something when you know it didn't work so great the last time you had it. i mean, think of how many people you know who have sworn off tequila because of a bad night. it's the same idea. going overboard can sometimes make it easier to skip that thing the next time around.
2. offer yourself a choice: the donut that is here right now or your favorite chocolate truffles later. you do have to make the or option something that you really, really like that way you can tell yourself that you can have one or the other and it's easy to pick the later option because it is clearly superior. this does mean that you will sometimes have to go get the better option, but if you pick your better option wisely then that means you'll skip the donut in the morning because you're going to the candy store to get the truffles and then when you see what a snarl traffic is you'll skip going across town to the candy store and instead just head home. yes, sometimes you will make the full effort to go get the special item. but then you will also be spending calories on something you prefer rather than something that is there.
3. do the math. most people are eating around the 1500 cal range. for women, 1200 of those calories need to be for nutrient dense foods that contribute vitamins and minerals [1500 for men]. in general, the stuff that is lying around as free food is going to be at least 100 cals a serving. so if you're choosing to eat whatever happens to be lying around, you're eating your caloric deficit you need to lose weight. if you can easily look up the nutrition info for the actual item, compare that info to how many calories you burn while exercising. so if krispy kreme is what is left out, that's 190 cals for a donut. so figure out how long you would have to walk to walk off those same 190 cals. how long would you have to run to run off those 190 cals? how fast would you have to run? how many hours would you have to sit, typing at your computer to burn off those calories? swimming? gardening? showering? doing jumping jacks?
3b. since you are tempted all the time, at the very least start jotting down all these nibbles and grabs in one place. then track them. see that it's not just one fun sized snickers from the candy bowl, it's a snickers and five kisses and a donut and some of that struessel cake and look at everything that you are eating when you're not hungry as a whole. odds are the sheer volume of food that you don't really want will help you cut back at least ten percent of it. and use that math to help you pick better options or stay away. i mean, if you track it all together and find out you're eating 700 cals of random stuff that you happen by, odds are you can find better uses for those 700 cals.
remember, just because something is there doesn't mean you have to take advantage of it. you don't stop to use every bathroom that you see, do you? no. you don't stop at every gas station because it is there, right? grocery store? pharmacy? movie theater? shoe store? doctor's office? hospital? just because things are there doesn't mean you have to use them. they are there to get use of when you need them, but if you don't need them, don't use them at this time. in general, most things are pretty available. sure, if you're great aunt sue who is nearing 100 is baking one of her famous cakes, indulge. but little debbie/krispy kreme/snickers/[insert your issue here] are so common that you can have them any time you want. and they are unlikely to disappear entirely [look at twinkies]. this is not the last helicopter out of a war torn area. if your office has donuts every friday, it's fine to skip them today because they will be there next friday and the friday after that into the foreseeable future. and, in the event that your office stops buying donuts, odds are you will be able to find a bakery, a grocery store, and a convenience store on your way home to hit the spot, if not more than a few of those places where you can find donuts. you have to remind yourself of the plenty, which means that this time isn't special, it will repeat and it's not worth it this time, right now.
-google first. ask questions later.