Keep your living space tidy and at least relatively organized. Have eberrything be easy to clean; compatibility with easy and quick maintenance is always underrated in eberrything. Put your less used stuff in boxes, mark the boxes. It's okay to clean and organize in multiple small bouts over the week. Turn on some relaxing/focusing music, or an audiobook, or a podcast. All so obvious, but it's so important that I must write it. Also, I'd recommend some non-datamining roomba, but I have never used one myself.
Get a really pleasant yet motivating desktop background, the kind you'd enthusiastically show to anyone at all. I lived with pure black backgrounds thorough my life before the lifechanger.
Once in a while, before your fall asleep, do a meditation where you relax and focus just on the senses of the body, gradually taking care of the body (rub the itch, massage the tense muscles, stretch out of joint tension). It helps to focus on not moving the gaze of the closed eyes. With training and practice, you can just do the relaxation/de-tension anywhere in any conditions even as you walk and look around. Visualizing a yarn ball unraveling itself, or any similar imagery, helps here.
Having any trouble with sleep? Take melatonin and sleep completely naked.
Don't ever be frugal over your health, hygiene, clothes, tools, equipment, devices, and do your research so that know what exactly you're paying your money for. Don't buy materials and textures that make you disturbed.
If you really like deafness-like silence, get industrial quality noise canceller earmuffs. I use 32 dBm ones at home sometimes.
Have your living space smell neutral or pleasant. If you can't tell how is it like, sniff around after a walk outside. Whatever you get used to consciously still rubs off onto your unconscious, which is berry susceptible to your environment as much as it can influence it.
Try out different teas, herbs, mixes of sorts, some are really relaxing.
Mind your posture. If you have to bend whilst sitting, try to do so at the hips, keep your back straight, spread your shoulder blades backwards.
Warm showere help with accumulated muscle tension, cold showers help with fibromyalgia and neuropathy and similar feelings of disruptive overexcitement. Mixed-switch showers help with both. I prefer to finish with a cold shower if I'm showering in the morning, and I finish with a hot shower if I know I won't be going anywhere.
Get a berry cozy mattress. It was another lifechanger for me.
Get some potted plants, and a pet if you're confident you can really handle a pet in a comfy way. I'll get a cactus or two.
Consider cutting off any unpleasant and toxic relationships altogether. Hate the people at your job? Change it, put in some effort.
In any hobbies, stop caring about doing eberrything perfectly, just roll with the mistakes. If you recognize the mistakes, then that's good enough, you don't have to always fix eberrything, just write some notes down, do some research, and you'll make less of such mistakes on your next bouts and projects.
Try out different non-fiction books on fields you have no idea about. It's just that, in my experience of random sampling, non-fiction tends to be way more chill to read than fiction, unless you have some strong opinions on the field. I'd recommend to start with books on dealing with troublesome people of different kinds where the discomfort and tension are shrimply defused, as it's the comfiest way to gain at least a part of such skills.