I have trouble focusing on one thing when attempting to WILD or WBTB, or even just practicing my visualisation.

I see an image or a scene, and think my brain makes an endless amount of pointless and bizzarre connections which lead into a different scene or new memory, which then puts me in a new one from there. It's an endless loop until I fall asleep into a normal dream. My brain has worked this way for as long as I can remember, even in waking.
I try to focus on my breathing or heartbeat, but get distracted by one of the images and so spoil my attempt at staying awake.

I managed to Attempt a DEILD last night for the first time, woke myself up from a dream and realised as I was doing it, so I stayed still, my eyes did open briefly, but I felt the heaviness in my legs and tried to picture my dreamscape... I couldn't focus on anything because alli saw was an endless incredibly quick stream of flashing images. No matter how hard I tried I couldn't steady the picture to create a scene.

Are there any tips for improving focus, or is this normal. Do I just need to try harder, put more effort into focussing on something??