I agree that sometimes, as social beings, we feel the need to speak to others about our sufferings. I believe that this is done in the hopes that we can find one of two things: sympathy and/or empathy. In our sharing, we hope to find others who are sympathetic to our emotions. By having a person tell us everything will be okay, we tend to feel better bout the circumstances we find ourselves in.
On the other hand, our greater hope is that we find a person who can be empathetic to our circumstances. When one finds someone who is empathetic, we have found a person who has been through what we are going through. While sympathy is always good, one who is empathetic has, essentially, been there and done that. Their advice and reassurance tends to make a person feel more hopeful about what is to come.
Outside of that, there is the fact that by sharing an experience with another, we get a sense of relief from the confessional aspect of our conversation.