I like both. While my mood can improve a bit after hearing an uplifting song, in contrast to that; my mood usually doesn't get worse if I listen to a sad song. But, the main reason I listen to music is because of the pleasing melodies/sound of the song/structure, as well as the interesting subjects and atmospheres which allow for enjoyable escapism and entertainment. It's likewise to watching a horror movie or thriller which may be a little scary or thrilling in itself, but the watching of the film tends to not make me any more fearful of the real world than I was before I went and saw the film.
I do tend to gravitate a bit more towards sad songs when I'm in a similar mood, but when I'm in a good mood then any musical style which I've found a liking for at one point or another can work well.
I'm unsure if these sort of uplifting songs would be considered to be exactly joyful, but here are a couple uplifting ones which I like most of the message of (although I don't think I wholly agree with everything said, the songs still do quite a good job I think.)
Then I guess there's some stuff which is kinda stupidly silly/joyful sort of stuff which I like as a novelty, like Helloween's song "Heavy Metal Hamsters." Maybe that's more along the lines of what people see as simply joyful rather than uplifting/inspirational? Although I guess there's probably joyful music which is neither silly nor particularly inspirational.
I have some more slight qualms with this next song's lyrics than the two prior ones, but overall I think it's still quite good, and it takes a kind of, sorrowful at points but also uplifting sort of direction.
Then finally to share some sad songs which I've liked a lot, here they are in another spoiler tag.