Bear one another’s burdens, and so fulfill the law of Christ. (Galatians 6:2 ESV)
I believe that a burden shared with another seems lighter even if the other person does nothing to aid the situation. Just the simple act of "telling" someone what troubles you, will lighten your burden.
And if the other person prays for you, touches your hand or arm, and shows genuine concern, it feels like wonderful medicine.
Plus, the other person is also blessed by "helping."
I think that it is truly robbing yourself and someone else of a blessing by NOT sharing your burden.
Can you over share? Yes, I also believe that you can share too many details when maybe just a vague request will do. However, I, personally, am not a fan of unspoken requests because I don't know if the request is in the Lord's will.
So how do you know how much to share and with whom?
It depends on the nature of your relationship with the other person and how much they need to know to pray for you.