Poor or bad grammar when writing can lessen the credibility of the writer, it can also be distracting to the reader, it can change the meaning of the sentence. Sentences needs to be complete. Being complete means, having a subject, verb and a complete thought.
When the writing is clear, spelled accurately and uses correct grammar, it will demonstrate sentence skills. when the sentence demonstrate a complete idea or thought, the reader will not be waiting for another word. The reader needs to be able to follow the thoughts of the writer.
Sprinkle can be shower. Manage can be superintend. Panicking can be overreact. Stay calm can be serene. Difficult can be burdensome. And severe can be extreme or dreadful.