Ive been LDing for a long time now (over a year) and what iv found is that (with me at least) informed experienced LDrs are at a disadvantage, when thinking about what I can do in an LD I pull on past memories on what iv tried and failed (or succeeded) at, so if I want to have an LD tonight where I whip out a light-saber and go at it with Darth Maul on the death star (for any hardcore star wars fans, i realize he was before the death star ) but if I do want to do that tonight I immediately begin to think "how am I going to get there?" this brings up past experiences that say "teleporting to places you've been many times before is hard enough! much less to the death star" thus i say "dammit ill just fight him on my lawn" then i think "how will my mind ever make an accurate representation of Darth maul?" then that leads to: "ill just fight a random DC" and finally I think to myself: "my mind will never be able to create a light saber" and so instead of an epic death star battle with the evil Sith lord Darth maul using masterful Jedi light saber techniques, I have a lawn battle with a 2 year old using sticks I found lying around on the ground....
this was all brought about due to my giving up things that I haven't been able to do before, (or had extreme difficulty) the trick one must learn is to take every experience in the dream as a one time occurrence, no two dreams are the same, my mind isn't incapable of making anything, its much more powerful than I or you could ever comprehend (at creating dreams) thus believe you can do it, with no doubts whatsoever, and you will do it....

another thing, I had a dream last night (pretty low level lucid) where I decided to destroy some gas station pumps to see what my mind would create in them, (I was at a low enough level of lucidity to not "expect" something in particular) and my mind created it, except that's not whats so amazing, I then proceeded to different pumps not really thinking alot about what the innards of the pumps looked like, and i tore them apart, only to find that every pump I dismembered looked exactly the same (there were three bolted down metal sheets, the top sheets contained some computer chips/ pump lines [tubes], the middle had some more computer chips and the bottom had cash [quarters, dimes, dollar bills, etc..]) I then looked behind me and there were all the destroyed pumps just the way i left them.
my point is, in the dreamworld the master truth of the whole environment is that you get what you expect your subconscious is one hell of a machine, it can remember alot more than anyone on this forum gives it credit for, the only reason lucid dreams change so much is because you expect it to because its a dream (we're taught from a young age miraculous things happen in dreams) if one can dismiss the fact that "its just a dream" you'll find that your dreams can be very much like this stable environment that we call earth.

overview:
take everything in dreams as a one time occurrence, dreams aren't static things, they're very dynamic from night to night, from dream to dream.

don't expect monsters to jump out from under cars, or things to "magically" disappear just because its a dream

I know the two things above might seem to cancel each other out but what you must realize is that dreams are what you make them, that's the supreme truth, that's all you need to know, this post was just trying to explain what that means.