To relax, tighten up first
This is a bit counter-intuitive but can be very effective. You can even do this right at your desk. There are much more thorough techniques for your whole body, (see article below), but this is a good abbreviated version to experience a feeling of relaxation in your shoulders.
Ah yes, shoulders. One of the most popular places for tension to build up. Try these three steps:
I know this seems simple, and it is. So with a little practice you can really get good at it quickly. Then when you really need a quick relaxation, you can take just one minute to make a real tangible shift in your body and mind.
This has a bonus effect! Muscle memory kicks in and makes it even more effective. After you have done this for a while, the tensing up of your shoulders becomes a cue that your body/mind takes, and your shoulders and neck automatically relax. Think about that for a second. You are training your body to relax as a response to tension. That's a big win.
Related Articles that I recommend
How To Do Progressive Muscle Relaxation
“By tensing and releasing, you learn not only what relaxation feels like, but also to recognize when you are starting to get tense during the day.”
Being with Stressful Moments Rather Than Avoiding Them
"Put bluntly, when we use mindfulness to get rid of stress, we’re no longer being mindful."