No, it's just another meme. Most inspirational memes aren't particularly wise, they just arise/become popular for various psychological reasons. They're a lot like candy. In this case it simply comes from the fact that people don't like to hear others complain. But there are plenty of things, especially injustices, also plain inefficiencies, oversights, etc., that should be changed for the better, and people complaining is one way they get changed. Also people may want to complain just to vent, which is fine. Not all of life is things to be grateful for IMO, and if there's anybody who's grateful for everything it's limited to saints and sages..