If my body functions optimally, if my sleep is optimal, if I'm incorporating play and non-excessive stressors on my body, the end result is how well I interact with the world, and myself in general. So my "mood" is how I determine my success.
I used to judge my mood based on my social life. Now I base it on my holistic (family, physical, social, sexual, professional) life. If I have success in some of those things, I'll have success in all of those things.
Going Paleo and learning from all these wonderful people here gave me that little glimpse that I was the creator of my own misery. It is easy to live in misery when one knows others are creating it — what can one do? One is helpless. That´s why we go on throwing responsibilities on others, whether it is the SAD or the USDA or the FDA or our doctors..
Grok (borrowed from Mark Sisson) has revealed that life is a verb. Life is not a noun, it is really "living" not "life." It is not love, it is loving. It is not relationships, it is relating. It is not a song, it is singing. It is not a dance, it is dancing. Now I See the difference, Now I savor the difference.
I generally try to maintain a constant BF% (give or take 3% points) while improving on strength. If I do that, then I'm happy. I feel good about accomplishments, and striving to convince those who are high-carb/low fat of their foolishness in BJJ, Weightlifting, etc. Is what causes me to feel good.
I definitely agree with the posts regarding judging how one feels (and looks), but in addition to that I judge based on my annual blood panels from my endocrinologist. I want to see that my body is improving each year I have them taken.
I view success as my ability to adapt to my ever changing environment. I measure this using the following metrics: lab results, self experimentation and feedback from loved ones (ahem - how cranky or nice I am).