I'm new in the forum and beginner with lucid dreams as well even if I've done research on the topic. Now when I know something, I can recall a few times, when I possibly have been lucid.
The first one (which I can remember) happened a few years ago when I was seeing a nightmare and suddenly realised that this is a dream and I should not be afraid. At that moment I thought I must be awake because I could understand that I was dreaming (I didn't know about lucid dreaming at the time and I would think I was actually still dreaming) and obviously I lost the image quickly after that. However, I haven't had many nightmares after that or if I have, I've been able to tell myself it's only a dream and in some cases even managed to turn the dream into a nicer one but waked up after doing so.
According to the facts I have gained about lucid dreaming so far, this seems capable of being it, but I'd like a confirmation from someone more experienced.