Yoga is the perfect preparation for developing focus. During yoga class, you may focus on anything from your to-do list to your growling stomach, but until you focus on the breath and the details of the poses, establishing the link between the body and mind, your practice will not improve.
Consciously inhaling and exhaling will not only let you root each asana deeper, but if you can control the breath, you can control the mind. Even if you're able to keep your mind focused, be careful to fill it with positive, self-affirming thoughts. Any definitive statement that contains the words "I" followed by "must," "have to," or "never" should be eliminated immediately. Regular yoga practice can encourage this kind of self-acceptance and confidence.