And there's the obvious Lacanian interpretation; when we look in the mirror, we “assume an image".
What we see in our reflection directly informs our perception of ourselves, but what see in the mirror
is a fantasy, not reality.
The forest is a mysterious place; it's wild and untamed and primal. It has to be survived rather than simply endured. There's a reason why it is so often the setting in fairy tales and folktales. They are usually inhabited by mysterious creatures, symbols of all of the dangers with which the young protagonists must triumph over if they are to become adults. Think about it:
The wicked Queen orders the huntsman to take Snow White into the forest to be killed. However, he finds himself unable to kill her as she sobs heavily and begs for her life. She stays in the forest, befriending the dwarfs who come to her aid more than once.
Hansel and Gretel are led into the woods by their father at the request of their stepmother.
Little Red Riding Hood walks through the forest to deliver food to her sickly grandmother and meets the hungry wolf.
It's interesting that the forest represents femininity and motherhood, as a beautiful place in which life thrives and is renewed; all of the above stories have a female protagonist who meets danger in the forest, and two of the stories begin with a stepmother sending them into the woods. (By the way, I just happen to be posting this on Mother's Day.)