The advantage is that you know what the other is going through and there is more understanding. The disadvantage is playing off each others mood and can be triggering, but anyone's moods can be. It can be successful or not depending on how you handle it and can have pitfalls like any relationship. See where it goes as long as you take care of yourself first, and look for any indications were it not to become healthy for you but this is true for any relationship. It could work out really well though.