Try to describe your ideas on “paper” (or note-taking app) first before you start designing.
I almost always use words to “sketch” my ideas. Using a thesaurus, or a mind map is unbelievably helpful. Visual sketching seems very permanent at times. Since I love reading and writing, I find that writing descriptive words stimulates my imagination without using visuals that tend to be cemented into my mind and can leave me stuck on one idea. If an idea isn’t clear [to you] in writing it will never communicate as a design. Use words first, you’ll be surprised at the results.