Without proper alignment, depth of the posture is irrelevant. First focus on getting the correct alignment of the posture and when you have achieved this, the depth will come naturally. Try not to be concerned by where anyone else is in the class, simply focus on your own ability. Honor your body and acknowledge its strengths and limitations. It’s so easy to get caught up in the moment. Even those of us who aren’t particularly competitive may feel like we have to go as deep as the person next to us. But we don’t and we shouldn’t if it isn’t right for our particular body.
In Half Moon Pose, for example, even if you can only stretch a few inches, respect your degree of flexibility and resist any temptation to force or
Pay close attention to the dialogue of the teacher. It so important to really listen to the alignment cues that a teacher is giving you. Not only do such cues protect from injury and physical stress, but they will also help to train your muscle memory to do the postures correctly. With practice, eventually you will be able to feel it in your body when you are misaligned. There is a keen sense of postural awareness that is eventually attained, which some may consider an added bonus or peripheral benefit to the practice.
In an effort to take your asana practice into your daily life, try to be more conscious of your posture when you are off the mat. The next time you happen to notice yourself slumping over on the couch, take a forward roll with the shoulders, draw them up by the ears, and then roll them back down behind you, opening your chest. Perhaps even relax your face and try to take a few breaths with focus. As you practice asana, listen to the cues the teacher is offering you, and really try to understand them in a postural way. Stack the knee over the ankle when setting up Triangle Pose. Keep your shoulders away from your ears, chest lifted, crown of the head reaching upwards in Tree Pose.
Listen to your body. When you feel a sensation in your knee, back out of the posture. When you feel your breath shorten, come out of your twist a little. These little tricks in your practice will start out as enlightening moments of what it feels like to be good and aligned, but eventually they will become second nature, and you will adjust yourself instinctively.