Self-value is a far more useful construction than self-esteem. The latter is, at best, a function of what you think about yourself—mostly in comparison to others—or, worse, a depiction of your ego. Value is more behavioral than conceptual, more about how you act toward what you value, including yourself, than how you regard it. To value something goes beyond regarding it as important; you also appreciate its qualities, while investing the time, energy, effort, and sacrifice necessary for its maintenance. If you value a da Vinci painting, you focus on its beauty and design more than the cracks in the paint, and, above all, you treat it well, making sure that it is maintained in ideal conditions of temperature and humidity. Similarly, people with self-value appreciate their better qualities (while trying to improve their lesser ones) and take care of their physical and psychological health, growth, and development.
Now here's the tricky part. People with high self-value necessarily value others.
Although hard to see in yourself, you can probably notice the following tendency in other people. When they value someone else, they value themselves more, i.e., they elevate their sense of well being, appreciate their better qualities, and facilitate their health, growth, and development. When they devalue someone else, they devalue themselves—their sense of well-being deteriorates, they violate their basic humanity to some degree and become more narrow and rigid in perspective, all of which impair growth and development. In other words, when you value someone else you experience a state of value—vitality, meaning, and purpose (literally, your will to live increases)—and when you devalue someone else you experience a devalued state, wherein the will to live becomes less important than the will to dominate or at least be seen as right.
It's often hard to notice that you are in a devalued state because devaluing others requires a certain amount of adrenalin, which creates a temporary feeling of power and certainty—you feel right (although you are more likely self-righteousness), but it lasts only as long as the arousal lasts. To stay "right," you have to stay aroused, negative, and narrow in perspective: "Every time I think of him, I get pissed!" In contrast, when self-value is high, you can easily disagree with someone without feeling devalued and without devaluing.
The impulse to devalue others always signals a diminished sense of self, as you must be in a devalued state to devalue. That's why it's so hard to put someone down when you feel really good (your value investment is high) and equally hard to build yourself up when you feel resentful.
If you doubt the latter, think of things you say to yourself and others when resentful: "I shouldn't have to put up with this; I deserve better, just look at all the good things I do...." When you value others, i.e., when your self-value is high, you do not think of what you have to put up with and you certainly don't feel the need to list the good things you do. Rather, when confronted with life or relationship challenges, you shift automatically into improve mode—you try to make bad situations better.
The great swindle of devaluing others is that it never puts you in touch with the most important things about you and, therefore, never raises personal value. On the contrary, its whole purpose is to make someone else's value seem lower than your own. If it works, you're both down; if it doesn't, you end up lower than where you started. In either case, your personal value remains low and dependent on downward comparison to those you devalue, creating a chronic state of powerlessness in regard to self-value. The motivation to gain temporary empowerment by devaluing others occurs more and more frequently, until it takes over your life. This could be what Oscar Wilde meant by, "Criticism is the only reliable form of autobiography."
Valuing others makes self-value soar. It also carries substantial social reward; showing value tends to invoke reciprocity and cooperation, while devaluing inspires reciprocity and resistance. Worst of all, devaluing others makes us look for something to be cranky about, so the low-grade adrenalin can inflate our egos enough to get us through the day.