| Quote #1
if everything happens that can't be done (1)
This line sets up the world of the rest of the poem. Literally, everything is happening that can't be done. The world of this poem is full of impossibilities that have become doable, and which are actually happening, which opens up all kinds of doors for us readers.
| Quote #2
one's anything old being everything new (14)
Anything old, being everything new? This would be like your grandfather becoming a young boy again, or your old faded blue jeans becoming suddenly crisp and bright again. Sounds pretty impossible and otherworldly to us. But, then again, the world of this poem is a world of hyperbole and metaphor, so maybe our speaker is comparing the feeling of love he has to the miracle of the impossible happening.
| Quote #3
so world is a leaf so a tree is a bough (19)
Remember, nothing is impossible, so these lines could be literal as well as figurative. The world could actually be just a leaf, and a tree could be just a bough. Big can be small, and vice versa.