I think we all have stress in our lives, but to reframe your question, being any type of actor or an actress is additional stress because until you land "the big part" in a play or a movie there is a lot of uncertainty about your line of work.
You are essentially a freelancer (someone who does work on a case-by-case basis as opposed to having a guaranteed job at one particular place), trying to get recognized, which can take many years and your career may never pan out.
So you have to constantly keep trying to get connections and you are often only as good as your last acting job.
Being a great actor or actress is no exception because career trajectories can plummet as fast as they rise. There is so much competition that there will almost always be people willing to make as many sacrifices as you to get a job.
In Hollywood, acting is in theory a unionized profession but in reality this does not mean that all of the union members are able to find steady work.
There is definitely stress in being a great actor/actress. I met a "great" actor once, and he said he would practice days and months in front of the mirror, saying his lines, and feverishly trying to get the perfect voice pitch, facial expression, and body movements. He did all this just so we could feel closer to the emotions he was trying to portray in his character. He was obsessed with acting perfection, and any form of obsession is very stressful. But, he was great.
Truth be told, I think there's stress in being a "great" anything. If you want to be a "great" artist, prepare to spend 16 hours a day drawing and painting. If you want to be a "great" engineer, prepare to spend 16 hours a day coding. If you're worried about being stressed, then 9-5 (8 hours a day) is perfectly fine. You will be "good", just not "great". If you want less stress, then 4 hours a day will allow you to be "just ok".
You will need to focus on stress and time management. In order to manage stress you have to manage your time wisely. <span style="background-color: transparent;">You have to set a routine for yourself and stick to it for the most part. Once you get into the groove of a routine it will be much easier for you to manage your time and have enough time for everything you need to do (including relaxing). Make yourself to-do lists on a weekly basis, use Google calendar or a planner to keep track of events, deadlines, and due dates. In addition to setting a routine and sticking to it, plan out relaxing activities into your day. Or set aside a time, after everything is done for the day, that you can have "me" time. I have also personally found it essential to not only find time for myself but also make use of that time in a way that is best for me and my holistic wellness. I have found the HeadSpace app to be an essential tool in helping me relax and generally feel more relaxed throughout the day, Guided meditation, even if you have a busy schedule, will make you feel more at ease and relaxed throughout the day as a whole (not just when you have the time to relax and focus on that "me" time).</span>
<span style="background-color: transparent;">Set a routine.Use Google Calendar.Set aside Me TimeWrite weekly to-do lists and use a planner.Find a peaceful and restful activity that will help you feel relaxed.</span>