My common dreamsigns always disappear after I have discovered them

This is kind of annoying, and it almost feels like my dreams are trolling me or something.
The problem is this:
I can spot my dreamsigns quite easily, because when they appear they will be very common in my dreams, like appearing several days in a row - but as soon as I accept them for reliable dreamsigns and start preparing for them, they stop showing up!
Why is this happening?
It doesn't make sense to me, shouldn't my great efforts to recognize them the next night increase my odds of dreaming about them?
Am I just having bad luck, or is there any logical explanation to this?

Please help me with this, because it's kind of irritating.

Yes, I often wonder if my subconscious is just fucking with me.
Perhaps there are larger themes that link together the separate dream signs? Perhaps you could make larger groups or categories to identify them with?
Once you think you have things figured out, that is a good sign you don't have things figured out yet. Larger themes perhaps...