1. They’re often deflecting

When someone is secretly unhappy, you'll note how often they dodge serious topics and conversations, whether through comedy, sarcasm, or simply being dismissive. They no longer talk about anything significant in their lives, and they've stopped confiding in you for no apparent reason. Even if you are aware that they are going through a difficult time (for example, failing a class), At best, they will shrug, laugh it off, or make some witty remark that makes it seem like it’s no big deal at all to them.