You may be very lonely in love as a result of constantly wishing things were one way while refusing to accept how they really are. You have all these wonderful hopes and dreams for your intimate relationships, and then, time and again, they just don't happen. This, in itself, could lead to disillusionment, loneliness and self-doubt, but it's likely that those feelings existed before your love affairs ever started disappointing you.
You have a hard time being your own advocate in life; instead, you may throw your energies behind someone else, or behind a cause that's not particularly important to you. Could this be because it's too scary to throw your energies into yourself, your own life, your own causes -- because if you were to fail, it would be too much to take? Or do you just not bother because you're so sure things aren't going to work out the way you want them to? Either way, the result is the same: You don't put enough energy and positivity into number one -- you. And your love life suffers as a result. If you can convince yourself to push forward in love despite your misgivings, you may find that things eventually work out a lot better than you think they will.