That is a really tough question, one I'm sure most of us here has grappled with. I'm still trying to discover self-worth, but my current thoughts on it:

We were not born with a sense of unworthiness. We learn to devalue ourselves as we age and experience this world, which is harsh and complex. We believe the perceptions, ideas, opinions, thoughts, musings and conclusions of other people, even of society as a whole. Why do we think we're ugly? Because society has decided that there is a pretty. Why do we think our view of something is incorrect and even ludicrous? Because another person views things differently, and has criticized us as if our view is invalid and laughable. We learn to see ourselves as we relate to other people. But belief and focus on the perspectives, ideas, and opinions of other people, can make us lose ourselves. I lost myself and my own friendship many years ago, because I was told I was hideous, pathetic, stupid. I simply didn't try to measure up to society's standards - actually wasn't aware I was supposed to. That was my only crime. They made it their lives to measure up to society's standards. Their emphasis on it, made me lose myself, because I eventually believed I should put emphasis on it, too. Ever since then I have considered myself unworthy because I don't match this, don't measure up to that. I think self-worth comes from, at least partly, letting go of these images, these "shoulds."

It comes from finding the breaking point where we refuse to put up with crap any longer. Realising you deserve better than terrible treatment, whether from others or yourself. Finally standing up and saying, "I'm not going to take this!" Absolutely everybody deserves better than a situation that is miserable, cruel, and soul-destroying.

Finally, everybody has good qualities, that would be appreciated and loved by others. For example, if a boyfriend cheated on me, he'd have lost a woman of intense love and passion, fun-loving, flirtatious, and a supportive cheerleader. A best friend. These are worthy qualities, in my opinion, and if one guy doesn't value it, another would.