Improve your time management and organization skills.
Of the many things you can to in this area the best ones include getting a to do list that works, learning to say "no", asking for help when you need it, and stop setting unrealistic goals for yourself.
Whether you are feeling overwhelmed by the amount or work you have to do or if someone is "in your face", a good thing to do is to "breathe through your nose". You can't get as worked up if you force yourself to breathe through your nose. Your body simply can't maintain the same level of energy without that extra oxygen you get when breathing through your mouth.
Even a five-minute break will help. Get away from your desk. Go for a walk - outside is better, but up two flights of stairs and back down is good too. Getting more exercise in general will help you reduce your overall stress levels and that will make it easier to reduce your stress level at work.
Smile more. We all know laughter reduces stress. You will be amazed at how much more pleasant the people around you are when you make an effort to be pleasant yourself.
Rather than getting upset when others disagree with you, listen actively and find the areas of agreement. Be assertive and stand up for yourself, but don't be rigid.
Make whatever adjustments you need to the lighting, temperature, noise level, and other controllable factors in your office.
Realize that there are some things that just aren't worth worrying about and there are some things you just can't change. Don't waste time stressing over the things in either category.
This is another of the things you can do to reduce your overall stress that will have benefits at the office as well. In addition to reducing your stress, it will increase your energy level and your ability to concentrate.
or a friend. Having someone to talk to can take a lot of stress off you.
Spend more time with optimistic people.
Negative people will pull you down to their level. Choose to work with people who have a positive attitude instead.