Can you do it "on purpose"?
Did you do something to learn how or was it just something that you were able to do?
I've always wanted to be able to have lucid dreams. For a while when I was a teenager I was really into it and read all this stuff about how to do it and shit, but I never could... never even got close.
But a week ago, for the first time in my life, I had a dream in which I KNEW I was dreaming. I wasn't able to turn it into a truly "lucid dream" or force myself or the world to behave according to my whim, although I tried... but I was able to use it to subtly change how the dream played out.
Then, yesterday, I DID manage to have a real lucid dream. I was napping after work on the couch and drifting in and out of sleep and managed to get into an approximately "lucid" dream state several times. I was able to have a TRULY lucid dream, controlling my "self" and guiding them, for only a few minutes or seconds I(it's hard to tell in dreams... nothing significant happened), but I did learn that I was not able to have lucid dreams in first person -- every time I tried, what I got was something more like sleep paralysis, where I felt like a huge magnet was pulling me down, and I heard this deafening WHOOOOOOSH noise, and felt a bit disoriented... sort of like vertigo-but-not-quite. I was also aware the whole time that I was in a dream state so it didn't really freak me out because I knew what was happening BUT STILL...
I have no idea what happened to me in the past week that I am suddenly able to breach that gap between awake and asleep and manipulate it. It's pretty awesome, though. I think it'll take more practice before I able able to have truly lucid dreams where I can control events and settings and sensations at will.