Because newsletter templates are available in all variety of lengths and sizes, there is really no limit to the content that you could potentially write. Keep in mind, however, that you should probably keep down your word count to a level that people are comfortable reading. While you may think everything that you are spouting off is fascinating, it's helpful to first sit down and make an outline of what you want your main message to be, or what the major news is that you are trying to share.
You can use templates to help you get healthier. There are a couple of designs for a diet and exercise diaries and grocery lists. You can even create a household budget or a household chore list. Figuring out how long it will take you to pay of your home loan can be done using a Microsoft Word template. Seems like there might be template for every aspect of life.