Sometimes when someone comes to you with a problem or a struggle it can be helpful to give a personal anecdote so that they know that you truly understand. However, don't feel that you need to do this every time.
This can be seen as making the situation about you and that is not helpful at all. It can cause the other person to lose trust in you. It can also be seen as downplaying their situation. Unfortunately, I can't tell you exactly when it will be beneficial. You have to know the person, to an extent, and read the conversation.
Even if the other person may think that you are making it about yourself, be apologetic and refrain from sharing your personal experiences at the time. The reality is that we all can truly relate to one another, even if we don't share the exact same experiences. However, sometimes we don't have to explain how or why this is possible. First and foremost, just be present. Listen and comfort as best you can.
"In him we have redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace, which he lavished upon us, in all wisdom and insight" ~Eph 1:7-8
