Last year I got serious about trying to lose some weight. After literally a lifetime of neglecting my diet and exercise I was tired of getting fatter. So I've been paying attention for the last year and have lost 20 pounds. And I feel good about what I'm doing, think I can sustain it. My goal has been a permanent lifestyle change, not a temporary deprivation; so far so good.
The two steady drops at the start of the graph (8 pounds and 5 pounds) came from calorie counting, with a predictable 3 pound gain in the middle when I took a trip. Counting calories really helped me pay attention to what I was eating, to learn to moderate. But it's a daily bummer and a pain, so eventually I gave up on it.
I didn't do any specific dieting again for a few months but still managed to keep a steady weight. Then a few months ago I started deliberately limiting carbohydrates, particularly sugar, inspired by Good Calories, Bad Calories. That seems to be working for me, another 6 pounds, and it feels sustainable. I'm skeptical of the low-carb fad of the last decade but having a salad instead of french fries and avoiding fruit juice and coke seems to make a difference.
The one thing I'm not doing is getting more exercise. Honestly, I'm just lazy. Biking is the only exercise I ever did sustainably but San Francisco is actively hostile to bikes. But I need to find something physical to do, for my health if not for weight loss.
Fun aviation fact: every pound I lose is another minute of fuel I can carry in an airplane.