What I do is take a break and don't visit the site for a day or two. I'd also ask if the staff members who are dealing with burnout could do the same, stepping away for a very short period of time will help. I do this with running my websites and even just playing games or browsing the internet. If I feel like I'm not enjoying my time spent on things, taking a break helps. It is a good idea to give a heads up of course, you don't want to look like you've just decided to abandon your site.