Be bold...

Wikibookians are encouraged and empowered to be bold and to use their best judgment in making changes, adding and removing content, starting discussions when community input is needed or when decisions are not so cut and dry, and helping to make Wikibooks a better place. If you see factual errors in a book or module, an error in spelling, grammar, or formatting, please fix it! If you see ways to improve a book or module, do so! Permission to make improvements isn't required.

...but please don't be reckless

Wikibooks is a place where anybody can edit, and if you think that you can help the project, you are more than welcome to try, but don't be reckless either. If you would like to make drastic changes, sometimes it is better to start a discussion and reach community consensus beforehand. Even the best of intentions, however, may have unintended negative consequences. Be bold in making changes that need to be made, but also be bold in admitting your mistakes and cleaning up after yourself.

This guideline

Wikibookians do not need to be bold, but are encouraged to be bold, and should rest assured that bold actions made with good judgment will likely not be met with undue criticism. Other Wikibookians should assume good faith and avoid calling bold actions reckless, instead calmly pointing out any mistakes that may have been made in the process.