Someone passed on a copy of Fred Brooks' software classic The Mythical Man-Month to me. The introductory page to the chapter on progress tracking has this question and answer:
Question: How does a large software project get to be one year late?
Answer: One day at a time.
Small slippages here and there add up, and if left unchecked, they add up a lot.
But this is a weight loss blog, not a programming blog, so:
Question: How does a large guy get to be one hundred pounds overweight?
Answer: One ounce at a time.
I weighed 140 pounds at one point of my adult life, in my first year of graduate school. Through the next few years I put on some weight, had an operation to fix the effects of Crohn's disease, and subsequently went up to about 180 pounds. I worked off 30 pounds of that over the next year or so just doing a lot of cardiovascular workouts. Then I started writing my thesis and that took precedence. Then I moved to my current location. Then I got married. A year after I was married I was 210. Five years after that I'd crept up to 240. That's up 100 pounds.
One pound is 3,500 Calories. One pound is sixteen ounces, so one ounce is 219 Calories.
Each day that I consumed a can of soda, a beer, or a candy bar more than I burned off, I put on an ounce. One day doing this, and one day exercising a little harder or one day pushing that soda away, evens out. But when those offsetting days aren't there, that's when the weight creep shows up, one ounce at a time, and it adds up.
I gained this weight one ounce at a time. I have to take it off one ounce at a time, too.