Depending on what my "frame size" is - that is, whether I'm big-boned, small-boned, or in the middle - the supposed ideal weight for a man of my height is 155, 165, or 175 pounds. When I was at my peak weight of 260 pounds - not really all that fat compared to a lot of people, especially most truckers - I said to myself that I needed to lose 100 pounds, mostly because it was a nice round number which was close enough to the truth. I dropped 56 pounds the first year without any serious effort, but then the weight held steady, and what's worse, I decided to stop driving, mostly because I was tired of getting ripped off by my company, but also because I wanted to put the finishing touches on my novel and then get it sold. I'd need a lot of time to study up on how to do all that, and driving (especially without getting paid for it) was wasting that time.
So consequently, I started regaining some of the weight I'd lost. I knew what the problem was: I was starting to over eat and my activity level had gone down. Finally, I managed to get it under control by making some minor changes to my diet and my behavior and the weight started falling off again. Then we took a trip out west and I stopped the diet, thinking we'd be extra active to make up for it.
Tip: Don't take trips with people who can't walk more than 2 miles in a day and who want to start the day at 9:00 and give up on the day at 4:00. You won't see much and you won't lose much weight from activity. I expected the guy twice my age and weight to cause a problem, but not the guy half my age and weight.
But anyway, I regained about 15 pounds in just those 3 weeks, so I had to drop them again.