Happened to me yesterday afternoon, actually. I've had it happen three times now, unintentionally. First time was a while ago...I got excited too quickly and woke up almost immediately. The second and third times it was a lot more "stable".
The key to stability in a lucid dream, I've found, is that you almost HAVE to take an "active" role in stabilizing the dream. Your mind can re-create experiences, but doesn't do so well creating experiences you've never had before.
For example, if you've never driven a Ferrari, your mind would have trouble creating that driving experience...it would probably draw from other cars you've sat in/driven to fill in the blanks of the experience.
If you find the dream destabilizing, you have to actively envision sensory inputs that can create a stable experience. Again, for example, once I was placed out on a small island over the water...my mind was having trouble creating a stable image of being by the sea, so I had to actively work to recall details like light shimmering off the surface of the water, the sounds of waves lapping, etc.
That means the more vivid your experience in REAL life, the more vivid you can make your dream experience. It also means that if you aren't getting LAID in real life, you're not going to get LAID in your dreams, unless you make something up, and that will be a shallow substitute for the real sensations. If you're getting laid all the time, though, your mind will have plenty of experience to draw on.
I'm just so thoroughly amazed every time I realize I'm in a lucid dream, I've never been able to make much of a conscious choice with regard to actions. Once I start getting "used" to it happening, I imagine I'll have some more flexibility in architecting and interacting with a dream realm.
This most recent time was just yesterday during a nap. It was weird how I got there...I actively felt my mind "trying to wake up", but my body wasn't ready to yet. You know how sometimes when you try to tear yourself out of a dream, you THINK you're waking up but you're really still dreaming? That's kind of what happened. I tried to wake myself up and I thought I was pulling "through the fog", but I quickly realized, "hey, I'm still asleep".