"All of us carries a heavy backpack, when that backpack swaps with two beautiful wings, that's when we can (are allowed to) rest."
I guess this is a philosophical text. 'backpack' is probably a metaphor for our [not so good/ heavy] experiences in life. Don't know if 'swaps' is the right word, the meaning is "when the backpack change place with two beautiful wings..." Please ask again if the bridge is unclear!