Four short lines, and the speaker has already shut the door on you. They describe their own mind as "not a good place," then tell the reader not to ask about it: "Trust me you don't want to know." It reads like someone who has thought about opening up and decided against it.
What stands out is the mix of honesty and hiding. The speaker admits something is wrong, but gives no details. That could be to protect the reader, as if their thoughts are too heavy to share. It could also come from shame, or from being tired of explaining. The phrase "Trust me" is casual, almost offhand, which makes the warning feel more real. It sounds like something a person says quickly so the conversation can move on.
The mood is uneasy and lonely. The poem's bareness, with no imagery and no explanation, makes the silence around the speaker feel bigger. We're left curious, but also aware that we've been politely turned away.