One of the easiest ways to change the feel of a room is to move some furniture around. This can be a challenge if you live in a smaller home or apartment, but get creative and test some different configurations. If your furniture is really heavy, maybe sketch some ideas out on paper first. Even moving just one chair, a side table, the bar cart or a large houseplant is enough to make a room feel completely different.
This can also be done outdoors on your balcony, deck or courtyard if you feel your backyard needs some love.