I press my palms and bottoms of my feet against an angular surface and massage them in a rolling fashion, then just gradually work my way up my arms and legs. Crack the back and neck a few times, lay down with a cold drink and watch some funny YouTube videos.
I likely suffer from BPD and so I deal with everything in excess. When I'm stressed, I may eat or exercise excessively. Sometimes I'll take more medication than recommended too. The more healthy alternatives that I have, however, usually include distracting myself through cleaning, playing my Switch or 2DS, and listening to music that was popular in 2012.
I pretty much deal with every emotion in excess, so it's gotten hard to distract myself. I deal with symptoms of depression so sometimes nothing I do can really help for over time. One thing I try to make a habit if I'm stressed or am close to breaking down is close my eyes and try to imagine a soothing color, then hold it for as long as possible. That color is usually light green for me. If I'm depressed though, then that exercise doesn't really help too much. But then again, it's just there so I won't break down. If I'm feeling depressed, then I just stare into space lol. Trying to force myself to do anything just makes it worse.
I also play video games, read, vent to friends, or listen to music. Depends on the mood.
I usually relieve stress by doing something creative; painting, writing, or something else along these lines. Usually I just take part in a pastime that keeps my interest and helps calm me down. Animals are also a great way to relieve stress; they are extremely attuned to the emotions of the people around them, and I find that simply petting a dog or playing with a cat has a huge influence on how anxious I feel.
Mostly by listening to music. Taking an hour or two just to listen to certain songs, can really help me relax and relieve my stress at the same time. When that fails, I try working out, or even just driving around in my car.