Keep accidentally waking myself back up

This is my first time on this sub and my first experience speaking to others who also lucid dream/seek to lucid dream, so I apologize if anything for any unfamiliarity with lingo and any unusual descriptions.

I have been successfully lucid dreaming for the past 5 years, techniques all learned on my own. About once a week, I take a nap during the day either flat on my back or flat on my stomach. I close my eyes and lay as still as possible and, when my vision begins to go from the red-black of my eyelids to the deeper black of sleep (and start to feel my head “swimming” that also usually indicates I am beginning to fall asleep), I imagine myself falling forward into the blackness like it’s a pool of water and usually have a feeling of falling also. From here my dreaming reality is completely under my control, anything I want and choose. I don’t know if this technique is normal or not, it’s just what works for me.

In the past few weeks, however, whenever I get to the stage of feeling myself falling forward into the blackness I am sort of pulled back from it and begin to wake up again. It’s become pretty frustrating.

Does anyone know why this is occurring, where I seem to accidentally wake myself up? I have a theory that is because I am too aware of myself falling asleep and too eager to do so, so I am rushing to process too much. If this is the case, how may I prevent that while also maintaining control of the dreaming state?