As far as decor goes, there’s nothing that quite approaches the marriage of kitsch and cozy as CHRISTMAS LIGHTS. Once you no longer live in a dorm, I believe the accepted adult way of adding them to your home is with fairy lights—perhaps displayed in some sort of mason jar DIY situation? But outside of being put on a tree, I don’t think that Christmas lights should require a pretense. Over a bookshelf, strung with Command Strips above the couch, meticulously taped around the ceiling’s perimeter—it’s the familiar transformation of a space you don’t own, but would nevertheless like to make yours.
I recommend leaning in to it and attempting to read in a room lit by 150-or-so warm LED bulbs, even if you are old now and it’d be better if you had more light. It’s nice.