That makes sense, that it would be your subconscious alerting. In a similar vein, whenever I know I need to shower first thing in the morning (as opposed to before bed), I often dream of showering on the bed. Yes, like standing on the mattress on top of all the sheets and pillows and blankets. Or at least somewhere in the bedroom, like on carpeted floor next to wooden furniture. I HATE those dreams so much but they keep happening.