In some of my dreams a common sign I have is I'm looking for a clock, but I can't find one or the clock somehow "forbidden" to look at... I usually get some sense of excitement but don't remember what it was about. I think this was probably because I became lucid for a moment and then forgot about it for the rest of the dream.

Weird... thinking about this I must've had quite a few partly lucid dreams where I didn't remember becoming lucid.