Consistency is key for technical or business writers. The goal is to write the same way each time. (When I wrote marketing materials and work proposals for an engineering firm, it was sometimes difficult to make sewer lines or ditches sound exciting.) User guides are meant to teach your readers how to do something. Good technical writers use templates and style guides to keep their work consistent. There isn't a lot of wiggle room for creativity. None of my technical manuals or test plans had plot or character.

I think you should challenge yourself in your off-time to do other types of writing — poetry, short stories, novels... It keeps you charged. It's a creative outlet that you often don't find at work. And it makes you a more versatile writer.