We can’t change the organization we work for, either, unless we own it, but we can influence the mood and atmosphere there. If the stress is unbearable and we cannot exert the influence we’d like, we can also change jobs. That is a drastic measure to be sure. However, assess what makes your workplace such a toxic environment. Is it the work or is it the people? Can the stress be partly attributed to your reaction to what is happening? If your workplace is truly too demanding, then save yourself and find another place to work.
However, if you are stressed out because nobody has ever told you what is expected of you, then talk to your supervisor about what they expect of you. If you feel like you need more training to do your job, ask for training. Perhaps you can find a mentor, or a buddy, or perhaps your company will send you to external training. You won’t know if you do not ask.