Sometimes people don't think of themselves as having difficulties that warrant professional attention...until they've experienced a series of disappointing, tumultuous, or frustrating relationships.
You may notice that you tend to gravitate towards people who don't treat you the way you wish, or who are ultimately unavailable to provide the kind of commitment you'd like.
Of course, such experiences can happen to most of us occasionally. However, if you detect a pattern of unhappy endings and don't understand why your relationships are mostly unfulfilling, even while you're in them, psychotherapy can help demystify your bad romances (apologies to Lady Gaga).