It's perfectly normal that it doesn't come easy at the start. It takes some practice.
Every time you go to sleep you enter a trance state, when you feel like you are getting closer and closer to falling asleep your brain waves are slowing down more and more.
Also, every time you close your eyes for some time, you relax, and you start controlling your breath you are entering a light/medium trance state. Feeling the sensation of "falling down" helps, but from my experience it's not strictly necessary. Just relax your mind and your body. Control your mind. That's the priority. Getting frustrated and angry because it's not easy is the opposite of what you want.
Entering a trance state allows you to silence the left side of the brain and have access to your subconscious. It allows energy to flow much better and spiritual techniques work more efficiently. It makes it easier to focus. It makes you more spiritual essentially.
This technique is needed to be able to access the right side of the brain, interacting with our subconscious mind, which is responsible for our outcomes that we manifest in our lives.