Practice the PROCESS, not the product!  Every day, we are new and different human beings.  Our bodies and minds shift slightly. So do our voices. It's part of the beauty of being human. This is the same reason that delivering a perfect performance is an impossible challenge. Even if you ever gave one, it would need to change immediately. So, when you're feeling down before a show or audition, keep in mind that the process is always more beautiful than the product. Strive for your ideal performance, but remember that true art is created in soulful and audacious efforts you give each day. Falling slightly short may be the very thing that makes you a lovable performer...and a lovable human being.