You can fall out of a tree pose with ease, or with frustration and a sense of defeat. Just like you can take a spill in your life and decide to dust yourself off - with a chuckle or an annoyed grunt - and get back up, or you can stay down, lie there, and give up. It's entirely up to you. It's your life, and your practice.
Yoga Cures: Simple Routines to Conquer More Than 50 Common Ailments and Live Pain-Free (ed. Harmony, 2012) - ISBN: 9780307954862