BATHS. I didn't really like them at first but I tried to teach myself to enjoy them because, uh, I really need to learn how to relax. And now I have a solid routine that I can turn to when I'm feeling down or just have a free night with no plans.
I like to add epsom salts (good for sore muscles) and sometimes baking soda (good for smooth skin) and essential oils (good for relaxation and feeling fancy) -- though if you add oils to your bath you should make sure to also add an emulsifying agent! A lot of blogs etc will say you can just add the oils to the epsom salts but... others say that's not the right way to go about it (bc the oil just sits on the top of the water and is highly concentrated which can cause skin irritation), and I'd rather err on the side of safety. So I mix 10-15 drops of essential oils (lavender is a solid choice but there are tons of other good options depending on what you're going for) with a squirt of castille soap and swish it all around in a cup with a bit of water before I add it to the bath.
It also helps to put on some relaxing music (I used to use an underwater ambient noise youtube video when I was training myself to enjoy baths, but now I mostly don't bother) and dim the lights and maybe light a candle or two. Some people like to watch TV or read a book in the bath, and I'll do that on occasion, but I didn't do it at first since the intent was really to learn how to just sit with myself without needing distractions.
It can also be nice to do a face mask while you're in the bath! And sometimes indulge in some good snacks/wine/etc.
Then when you get out, lotion up and crawl into bed!