You’re not responsible for meeting this man’s needs. You don’t need to trick him. “Please leave me alone.” If he does not do this simple thing, then you have not committed any offence and you can train yourself not to feel bad about it. You already meditate, so you might make your tendency to feel bad about this into a object of meditation.

Unfortunately, you can’t control his behavior. He might still try to sit down next to you and talk to you about things that don’t interest you. I don’t know what more you can do than ask him to stop doing this and hope he complies. “Please stop doing this. I’m just not interested. I prefer to be alone.” It is compassionate to say nothing more than this.

As for why you’re like this, that’s very likely because someone taught to you to care about other people’s feelings and didn’t teach you that their feelings are not your fault. This seems pretty common.

The stories you tell yourself about why he does this and the stories you tell yourself to explain your own behavior… they probably don’t help you much, do they?

Peace.