There are so many aspects of life outside of your sphere of control, and actually the case could be made that this fact is the source of all anxiety. If you had the power to manipulate everyone and everything you would be a god and there would be no reason for you to feel anxiety since even if you did perceive the world as hostile you certainly wouldn’t feel helpless in the face of it.
But you’re not a god, you’re a human being, and no matter what you do or say you can’t always control the things that happen to you, the way others feel about you and treat you. One thing you can control is your yoga practice. During that hour long session your mat space is yours and yours alone, you have the final say over what happens on it within the limits of your ever expanding ability to manipulate your breath, body, and mind. Regardless of how far you can go into a pose, you always get to decide how much effort you’re going to exert, when to go further and when to back off, when to keep powering through and when to take a break. This process is not metaphorical proof of your personal power but concrete proof of your personal power.
You can take that experience with you into the rest of your life, realizing that you control your thoughts and actions and this is the source of your power. And while you can’t control outside stimuli you do always retain the power to respond to these stimuli as you see fit. That burgeoning sense of power you feel over your mind and body on your mat during sessions is armor against the anxiety that arises from all the elements of life you can’t control.