I've had two lucid moments in the last fortnight and BOTH times I stopped stabilizing my dream because I thought I was performing the action in real life, which would mean I'm already out of the dream. But both times I wasn't.

From my DJ:

But in the middle of the road, the old lady who crashed says "Here he is; the boy who was running on the road!!"
I think to myself Why was I running on the road, if I wasn't supposed to?
Oh, I'm dreaming!
Immediately all the people froze. "Okay, I can't panic or I'll wake up. What am I supposed to do? Stimulate my senses!"
I stare at the road, which gets really detailed, but it's not enough. I decide to clap three times, but as I do, I can hear it echoing around my bedroom. I thought "Oh, it's too late. I'm going to wake up." Everything goes grey.
I see the word ALLUSION for a second.
I wake up.

After about 30 minutes I realised Wait a second, I have a cast on, I can't clap!
The claps really were in my dream, dammit >
I realized I was dreaming for real. Everything was white and i yelled "increase clarity now!" three times and rubbed my hands, but again, it felt like i was doing it for real in my bed and that it was too late.