I feel the cover doesn't work because of the message you're trying to convey.
This is supposed to be an inspirational book. It's supposed to motivate, help clarify, and give direction for writers.
What it currently looks like is something you find in an attic, something from a thriller. Generally it says "messy/uncontrollable/chaotic." The tilt of the paper, the splotches, the aged paper all convey the exact opposite message I think you're trying to target.
I would work it from a place of bright, powerful, good feeling design. Go with a positive colour scheme (blues, golden yellows, earthy greens), use images that make the writer feel good about what they do, and are ready to take on what you're providing them.
Aside from that this cover in general feels empty. As the title is what is the focus, instead of like a fiction book where you can use an image to carry the message, the title needs to be larger and be a main element. It should be taking up the entirety of the piece of paper. At the moment I'm expecting something else to be at the bottom section of the paper, and the post it note isn't enough.
I hope this helps! As ever, take what feedback works for you and leave the rest