> it did not justify the hundreds of hours I invested in this project.

I agree with this but minimizing the cost changes the ROI.

Personally, I've discovered useful insights tracking various life metrics. But I also found quickly diminishing returns after a few weeks or months -- if an association isn't obvious within that timeframe it's either too much effort to isolate or too slow or small to matter.

At various points I've tracked calories, macronutrients, weight, allergens, supplements, sleep, exercise volume, exercise timing, nighttime screen use, spending/budget, air quality, and mood. Now I know what kind of cooking wrecks the air quality in my house, what foods I don't digest well, what various protein/carb/fat ratios look like on my plate, how much effort it takes to improve fitness, that exercise in the morning or early afternoon improves my sleep while exercise in the evening harms it, and that any alcohol or caffeine wreck my sleep while screens at night have no measurable effect. But once I understand the associations I can alter my behavior and move on.

> The whole "quantified self" movement might be more about OCD and perfectionism than anything else.

I would agree that continuing to track metrics every day long after they've stopped yielding new insights is often compulsive behavior. But I think that's an argument for time-boxing experiments, not necessarily avoiding them altogether.