I lost 25 pounds this year so far. I plan on losing another 20 to be my ideal. I have the feeling it will be much harder than the first 25. I did it by taking about 3 months to develop good habits of eating before I dieted. It helped so that the very hard work of the diet felt much easier and that if I fell I know I could fall back to something where I would still lose weight but very very slowly. There is so much hard about dieting that it helps to not be thinking about milanos or cookies when you are trying to avoid sandwiches.
That skip the mayo stuff puts the cart before the horse. You need to make the I-am-going-to-skip-the-soda-or-the-mayo decision-making to keep weight off, but it muddies the issue up of how to actually get to where you want to be (unless you are only a few pounds overweight). I just think that kind of decision making should be put into a context of decisions you make because you don't hate yourself rather than the context of make these decisions and you won't hate yourself.