Scale is the number one area where most people make mistakes decorating their home. It takes a trained eye to design a properly balanced room–the kind of Goldilocks-style oasis where everything looks and fits just right. If you don't have a trained eye to take with you every time you go shopping, you can at least take some advice: Go up or down a size when you buy these four decor pieces.
What You're Buying Too Small
Big decor comes with a big price tag, but proportion should always be your first priority when you're sourcing these three accessories for your home. If you need to save up for the right size, save up!
Huge rugs are expensive, and it's tempting to scale down to a 5'x7' in the name of saving money. But really, you're not doing your room any favors. The $100 or so upcharge for the next rug size up is a small price to pay for not hating your home. Most living rooms need at least an 8'x10'–if not a 9'x12'–for maximum domestic harmony.
There's nothing wrong with bare walls, but you want the walls you do decorate to look intentional and, yep, well-balanced. A general rule of thumb is art should be about half or 3/4 the size of the wall it's on, but multiple sources suggest .57 is the magic number. So if you have an empty wall that's 120 inches wide, you multiply that by .57 to find that your art should be roughly around 68 inches wide. That means one large 40"x60" print would fit well, as would a gallery collection of multiple frames that add up to about the same size (when you measure them all together, including the space in between).
Lighting may fit into the below category for some people (i.e. they're buying too big), but most home decorators buy up lamps and light fixtures that are too small for the space where they're going to live. Table lamps should be tall enough that the bottom of the shade is at seated eye level. And a pendant above a tabletop (like a dining table or kitchen counter) should be big enough to visually balance the surface below it–around 12" smaller than the diameter or width of the table or counter.
What You're Buying Too Big
Unless you prefer an overstuffed aesthetic, this is one area where bigger isn't always better:
There should be enough empty space around the furniture in your living room to create movement and facilitate flow. A small room demands a small sofa, no matter how much you're craving a massive sectional to lounge on. Buying a too-big sofa also forces you to push it against the wall, meaning that floating furniture in the center of the room (much advised for a cozy setup) becomes impossible.