Try and read a good fiction book. Reading and creating the images in your brain opens up some of the same neural pathways that you use for dreaming, so it gets you into the right state to nod off

Also, if you wake up in the middle of the night, don't lie in the dark and let your mind wander on to stuff that may cause anxiety, it wakes up the wrong part of your brain. Switch the light on and read for 10 minutes, immerse yourself in that book and I guarantee you'll nod off again sooner