Here are a few hints about writing papers and grant applications.
First, just do it! Start writing. Worry about all the details on the second and third rewrite.
Second, review every single sentence. Is each sentence actually true? Any claim needs to be backed up with evidence (e.g., a reference). Never offer undefendable ground. In my view, far too many papers contain assertions that are debatable. For example, "this experimental data proves theory A is correct" should be replaced with "this experimental data is consistent with theory A".
Third, reconsider qualitative language and value judgements. You may write "the agreement between my theory and experiment is excellent" but others might think it is not particularly impressive. Perhaps it is better to be more circumspect and write "the theory and experiment are compared in Figure X" and let the reader make their own judgement.
Fourth, avoid vagueness. Be concrete, precise, specific, and informative. Instead of writing "there are lots of different theories of high-temperature superconductors" write something like "the diverse range of theories of the phase diagram of cuprate superconductors include theories that focus on resonating valence bonds, antiferromagnetic spin fluctuations, van-Hove singularities, quantum critical points,...." and give specific references.
Fifth, get feedback from others.
Sixth, keep at it. It is hard work, even for the experienced and gifted.