The first thing I do with a living room curtain is pinch the fabric and hold it up to the window. If light comes through it like a bedsheet, that tells me everything about how it will hang and how it will age.
There are rooms where curtains are flatly the wrong answer, and I think people forget that. A living room with a gorgeous original window, nice proportions, decent moldings, can get smothered by heavy drapery that was really designed to hide a bad view or block a streetlight. If your windows are the best thing in the room, sometimes the right move is almost nothing, a simple blind or no covering at all, and let the frame do the talking. Curtains also struggle in small rooms with low ceilings, where a floor to ceiling panel just eats the space and makes everything feel like it is being held up by two columns of fabric. And if you have radiators or a reading chair tucked under the window, pooling fabric on the floor there is asking for scorch marks or a permanently crushed hem, neither of which looks intentional.
A well made curtain tells on itself the second you touch it. Good ones have real weight, a cotton or linen with some body to it, or a proper lined fabric that falls in soft, heavy folds rather than clinging to itself like a shower curtain. Cheap ones feel thin and slightly stiff at the same time, which sounds impossible until you have handled enough of them. Look at the hem, it should be generous and evenly sewn, not a thin rolled edge that will fray the first time it goes through a wash. The heading matters too, whether it is pleated or tab top, the fold should hold its shape on its own when the curtain is open, not flop sideways like it is tired. And the lining, if there is one, should be sewn in rather than glued, which you can tell because a glued lining eventually bubbles and separates in patches that look like a bad sunburn.
Where curtains fight themselves is pattern on pattern, a bold curtain against a busy rug or an already patterned sofa, where the eye just gives up trying to find a place to land. Keep one of those elements plain.
This is the right call for a living room that wants to feel settled and a little soft at the edges, the kind of room where you actually sit for hours, not just pass through.