As it pertains to my box, God gets to hold it. We open it up together, and I bring each item to him. When others share their boxes with me I get to watch as they unpack, and validate what I see. Why would I try to pick something up that God already is holding?
Do you feel responsible for the hardships of others? You're not. It is so important to be there for the ones The Lord has placed in our lives. And when its appropriate we should speak into their lives with grace and truth. But more than anything I believe that making room for Jesus to be Jesus gives miles on end for me to be me, and the other next to me to be them.
I believe carrying someone's burdens is very different than trying to fix their burdens. I'd much rather sit with someone in their pain and see them, rather then try to fix their heart and life circumstances. I believe that Jesus came to heal us, and set us free to live for Him. It's His job to heal the broken parts of me, and comfort me. And that doesn't change for the other beside me.