Sounds like you are mixing WILD where you enter the dream from Mind Awake Body Awake to Mind Awake Body Asleep as you fall asleep
but for WILD most people would sleep for like 5hrs or so then wake back to bed and remain active (mentally if not both mentally and physically) then they wouldn't so much do mantras as try to hold vaguely onto consciousness. I have achieved Dream Exit Induced Lucid Dream (DEILD where your in a dream and wake up and then go back into dream in WILD-like fashion) but never succeeded in a direct WILD, tho I have made it to full paralysis many times

You seem to be mixing this with DILD (Dream Induced Lucid Dream) where you also might wake back to bed or train yourself to wake after every dream (possibly to DEILD but more likely) to do mantras and say things like "dreams are important" "I will remember my dreams" "I will be aware I'm dreaming" "I will become lucid" or whatever. Then after you fall asleep you dream (like always), but have increased chance to become lucid (become aware your dreaming). The difference is in this case you go from Body Asleep Mind Asleep to Body Asleep Mind Awake.

read up on DILD and WILD and see which you think you should try first. If you want to have lucid dreams go to sleep early and get lots of sleep. And nap often, this will increase your chances.