Sometimes people's ability to feel confident gets sabotaged by subtle (even unconscious) irrational beliefs they may hold such as the popular belief that “if people don't like me it's because there is something wrong with me”. Such a belief is irrational because one statement doesn't follow from the other, and because there is no evidence that either statement is realistic. People who hold this belief inevitably find the process of dating to be painful, as they take every rejection personally. They conclude that since everyone should like them, that they must have a fatal flaw that caused them to be rejected. Sometimes this false conclusion gets over-generalized to an extreme and people end up concluding that they will be 'alone forever'. It never occurs to such people to wonder whether there was something wrong with the people who rejected them. In reality, different people like and are attracted to a wide variety of different personality and body-type characteristics. The selection and rejection process that takes place early in relationships is less a reflection of one's personal worth and more a statement about a rejectee's personal taste (or lack thereof). If someone rejects a person because that person is too thin or too heavy, too religious or not religious enough, or too 'whatever', they have actually done that person a favor by saving them from the company of another who is not interested in being a partner. Being rejected by someone who is not interested in being a partner frees a person to pursue a relationship with someone who is interested in being a partner. While being rejected by someone (or rejecting someone yourself) can be very painful and lonely in the moment, it is preferable to getting intimate with someone with whom you are ultimately not compatible. It is much harder and more painful to end a long-term relationship than a brand new one.
The prospect of being rejected is not a pleasant one, but most people are able to tolerate it to one degree or another. A minority of people are excessively fearful of being rejected or negatively evaluated by prospective partners to the point where they are simply not able to be confident at all and avoid dating altogether. If this description fits you, don't fret. You may have a very treatable condition called Social Phobia. Excellent (cognitive-behavioral) psychological help (and medical help too) is available. We encourage you to seek it out.