A teacher can encourage students towards a positive attitude, as defined from a Yoga perspective and guided by the yamas and the niyamas, leading students towards a non-harming, non-grasping, focused Yoga practice. One of the key things I have heard teachers remind their classes is that a pose is not about results but about effort. Being in touch with your body and putting in the right amount of effort in a way that challenges you while respecting your needs and avoids the risk of injury is a key ability to develop a balanced practice.
Most importantly in the Yoga studio, though, is the teacher's attitude, because this sets the pace for the entire class. A Yoga journal article for teachers (http://www.yogajournal.com/for_teachers/2610) expresses this perfectly by reminding teachers to pay attention to their posture, since the way you carry yourself is the first thing students will notice as they come into class. Body language can be a simple yet powerful tool to create an atmosphere of trust and comfort for a new student.
Much of a teacher's attitude comes from their own history and personal approach to Yoga - are you playful or serious, quiet or vocal, lenient or strict, or somewhere in between? For me, the most important thing for a teacher to consider is whether or not they are acting according to the principles of Yoga. Are you teaching from your ego, seeking acclaim or admiration from your students? Or are you allowing knowledge to be channeled through you, teaching from a humble standpoint instead of grasping at results?
A recent experience I had puts this in point for me: the other day I was leading an informal group of Yogis who wanted to try salamba sirsasana, supported headstand. As I explained the steps for coming into the pose against a wall, I decided to demonstrate the pose, but it was hard for them to see me with my back against the wall. Acting quickly, I decided to demonstrate the pose in the open, re-positioned my mat, and lifted up. All good until I remembered where I was, and with a sudden loss in concentration I promptly fell straight over backwards with a resounding "thump"! Thank goodness the group was not scared off the pose and after some better instruction had a very rewarding session in headstand!
These are the moments that Yoga teachers dread... yet in these moments we also learn the most about ourselves, and that is Yoga. In reflecting on this quite embarrassing situation, I realized that the primary thing that went wrong that day was that I did not have the right attitude. I did everything I told my students not to do. I didn't take time to prepare for the pose. My concentration was elsewhere. I was focused not on my breathing and the pose but on the group. But more than that, I was over-confident, and took the opportunity to show off for the group. Falling over was a 'tiny Karma' - in other words, I deserved what I got! So, I learned a valuable lesson - and few bruises!
However, at least I can honestly say that I demonstrated positive attitude after the fact. I did not allow my ego to take over, despite being somewhat embarrassed. I laughed heartily at my mistake and assured the group that they would be safe since they had a wall to support them. For me, it was a good reminder that Yoga, like life, is trial and error. We make mistakes, we fall down, both on and off the mat, and it's ok. A Yoga student should never feel judged by a teacher's attitude. While perhaps other aspects of our lives are not so forgiving, a Yoga class is a safe space, where the student is respected no matter where they are with a pose, as long as their intentions are good and they are putting in the right effort. And every once and a while it's good to know that even our teachers make mistakes - and learn from them. I know I did.