[throwaway74432]

It sounds like you want someone to agree with you that your memory plus your subjective view of yourself is a "good measure" of progress, despite the existence of scales and measuring tapes, which dwarf your subjective memories in terms of reliability and accuracy. We'll just have to agree to disagree.

[lapcat]

It's really not that complicated. I can tell a lot of things by looking in the mirror. That I need a haircut. That I need a shave. Despite the fact that I've literally never used a measuring tape on my hair. That my hair color changes slightly (lighter or darker) with the seasons. That my hair has gotten grayer with age. (I would prefer to deny that, but eyes can't actually lie that much.) I can tell if I'm sunburned (I never tan, sadly). And yes, I can tell that my stomach has gotten thinner or thicker over time. These are not exact measures, but you can in fact reliably tell when your body changes. Subjectivity is not blindness.

By the way, your previous comment was flagged dead. You might want to reconsider the way you reply in light of that.

[throwaway74432]

You're right, it isn't complicated. The beauty of a true good measure (ie, a scale or other measuring device) is that you can track actual discrete progress over a very short time span. If you didn't know your hair grew, could you track the amount that it grows in 24 hours by looking in a mirror? With a measuring tool, you can. That's a good measure. Compared to it, looking in the mirror is a poor measure. That's why scientists use measuring devices when trying to track quantities, instead of "eyeballing" it and claiming its good enough because they noticed some change.