Hmm, I agree it can be quite difficult sometimes, but you should eventually fall asleep. I doubt I'm thinking single-mindedly on remembering my dream when I'm at the verge of falling asleep, because if you were able to do that, you would probably enter the dream consciously (WILD). In other words, it's difficult to focus on remembering your dreams all the way until you fall asleep, your mind will eventually drift off. Maybe it helps to concentrate the focus only on the dreaming and try to forget about the sleeping?

And welcome to the forums, by the way