Why to the words and opinions of others hurt us?

If we were completely secure in ourselves, so much so that we had total and unshakable belief in what we knew, and who we were, then why would the opinions and harsh criticisms of others bother us? Why are we so insecure,and need to be supported by another emotionally? If we truely need something from another, and by this i mean anything that gives us a sense of completion and security, and if we rely on this, so that without it we would be somehow weakened, and feel vulnerable, or unloved, then how can we think that we are whole person ? All emotional support that we need from others, is a compensation for our lack of self belief. To really understand the meaning of what it means to have love, we cannot need emotional love from another. To give offer anything of worth, and lasting value, in a loving and deep sense, one has to be full, and whole. How can a pauper give of his riches, if he has not a penny to his name? It is the same with us, when we think that we love. But unless we come from a place within ourselves where love reigns, then what we give is nothing. We actually need from others, the very things that supports the illusion that we have self worth, we need ego support to continue in this backwards way of life. Once one understands this, life becomes so much easier.