Calm in a room is mostly about editing, not adding. Five quick moves:
1. Take the light down to knee height
Overhead light flattens a room and keeps you alert. One or two low, warm sources — the candle warmer, a sunset lamp on the floor — change the whole mood in seconds.
2. Clear one surface completely
Pick the surface you see first when you walk in and take everything off it except one object. Somewhere out of sight to catch whatever you just moved helps it stick.
3. Add a slow-moving thing
Something with gentle motion gives your eyes somewhere soft to land: the mist and flame of the diffuser, the falling smoke of a backflow burner, or a slow galaxy from the projector.
4. Put weight on the sofa
A soft, substantial cushion or two, actually used rather than arranged, makes a sofa read as somewhere to rest rather than pass through.
5. Deal with the cables
Bundle the visible ones, tuck them behind a leg, hide the power strip. It is a small thing your eye stops snagging on.
Ten minutes, no purchases required for most of it. The room will feel different when you sit down tonight.