I have never considered therapy - I tend to overthink everything anyway and the last thing I need is encouragement!
I always imagine a therapist would be like your "sweet" friend who is sooo sympathetic when you have problems and wants to hear the whole story, while secretly revelling in the whole situation. Apologies to any therapists on GN, that's probably totally unfair, but I really don't understand why anyone would want to involve themselves in others' problems, unless they were close friends or family. I remember Roger Moore's comment when asked about his seemingly sunny personality and untroubled outlook on life. He said, "The trouble with sharing your problems is that 90% of people don't care and most of the rest are glad you've got them", A little cynical, perhaps, but I have to admit that's pretty much how I look at it.
I don't think many people set out to cause hurt and distress in relationships, but reading some of the threads on GN, it seems that most of the problems are caused because someone else has not behaved as the particular poster would like them to. In my own relationships, I tend to cut other people as much slack as I can stand to, but beyond a certain point I do stop contact with them or keep it to the absolute minimum possible. We can't dictate how others should behave, but if they cause us distress, I don't think anything is gained by endlessly analysing their reasons for the behaviour or explaining to anyone else why it upsets us so much. Some relationships will never work well because of the personalities involved and sometimes we just have to accept that.