Password that which you want kept secret. When writing is not forced it tends to be better. There are virtually no laws prohibiting content in writing. The problem is not that you will write x-rated but that you will write like a grade schooler. Stilted writing styles infer rigidity and close-mindedness.
Stilts impress no one anymore.
Avoid using too much jargon in business letters. It's not just that jargon is boring and shows lack of originality but more importantly the reader may not know what the jargon means. If you write for yourself it is therapy. If you write for others it has meaning for them which is also therapy for you. Frankly writing is one big mystery.