Load up your idea catcher. When you have an inspired idea about something you want to include in your next issue, plop it in.
This works really well if you regularly include popular quotes, blog posts, book recommendations, and other resources. As soon as you come across ones you want to use, ‘catch’ them.
By the time your issue date rolls around, it won’t seem like such a chore to assemble your newsletter. The bonus of this approach is that you have less stress trying to remember all those great ideas!