Before I knew what lucid dreaming was I remember on occasion I'd have dreams where I knew everything would be okay when I woke up. From my recollection they were all nightmares of one sort or the other. I also remember I didn't have any ability to deviate from the dream whatsoever. I guess they were lucid dreams or at least semi-lucid or just a very low level of lucidity, but I suspect some form of LD.