Every time we come to the mat, we are teaching our body patterns of movement. Similar to our patterns in the way we think and act on a personal level, we can discover that the same can be said in our yoga practice. Make a habit of looking for blind spots. In which postures do you feel unsure? Do you stop and address this uncertainty or do you move to the next posture (putting that one on the shelf)? Awareness of our movement patterns is an integral part of our practice.
A common place of tightness is in our front body, specifically in our pec major and minor. Adding a few minutes of opening these muscles can help the scapula move in a healthy way along the upper back. When we lift our arms above our head (downward facing dog, warrior one) or when we are pressing down in plank, we want our scapula to protract a little from the spine and rotate upward. If the chest is tight, this movement can be restricted.
Place a block under the scapula with the block on its shorter side. Then, externally rotate the arms and let the elbows rest on the floor. If they do not reach, put blocks or blankets under the elbows so they do not float. This assisted pose is a great way to open the pec major and minor. Next, you can try bringing the arms over your head by way of external rotation. When the arms are over your head, please make sure that they are fully engaged and full of life.
Once you have really FELT this, take this sensation and see if you can bring it into your warrior one pose. Play with the visual of expanding in all directions while in your postures.