The way I like to explain meditation aimed at samatha it is that your mind is like a busy room full of conversations, and as you meditate, the conversations go

The way I like to explain meditation aimed at samatha it is that your mind is like a busy room full of conversations, and as you meditate, the conversations go quiet one by one, until there are just a few left. The ones left, the stubborn, uncooperative ones, are often the least pleasant. They are the ugly thoughts, the scary thoughts. And because you've let all your other thoughts go quiet, the unpleasant voices are now filling up the whole room. Before, you might not have been able to really hear them over the noise, but now even whispers ring out loud and clear. You can't make them shut up, and you aren't supposed to initiate new thoughts to refute them. You are only supposed to observe. In this way, a meditation session can, on a bad day, turn into sitting and listening to all your worst thoughts echo inside your head, not through any mistake, but as a natural consequence of how meditation works, especially for a beginner. I don't know of any traditional meditation practice that claims to provide immediate benefit for a novice. It is presented as a skill that yields results through sustained development and practice, and difficulties are expected along the way. People presenting it as a quick and easy way to improve mood are the same kind of people who promote fad diets.