As your brain slows down into the deeper phases of sleep you tend to lose more control; lucid dreams will generall be shaped more around the light sleep (and also more easly influenced by the outside world).
You forget your deep dreams is because when your brain start speedin' up slowly and goin' into different phases of sleep, different dreams and switchin' to a more conscious state of mind; tryin' to remember through all of that is nigh impossible.
But as you say; an alarm clock or someone slappin' you awake will skip all the hassle of your brain havin' to slowly speed up and change; you'll retain a memory of thr dream...but not for long.

This is also why folk are usually pretty slow on mark or grumpy in the mornin's...they're brain is quite literally not functionin' at full capacity yet; especially if they got woken up unnaturally.

Quote Originally Posted by Tricky Boy View Post
I never dream... ever... or at least I don't remember in when I get up...
You dream about five times a night; you jus' don't remeber.
Do you tend to get pretty uninterupted sleeps and a decent full night of sleep, then?