We have a project we're doing for school that's supposed to be done before the summer. Since we are both in school we can't really work on this project full time and therefore when school floods with assignments and homework, the game kinda gets pushed to the bottom of the priority list (at least for me, I usually spend the weekend with my gf and family, while my friend is working on the game).
But this weekend was amazing, we had the biggest productivity spike ever, we made more commits to our repo this weekend than any other previous week. We got a lot of work done and we had a whole bunch of fun. It's harder to slack off when your partner is sitting next to you. Plus, whenever you run into a problem it's really simple to just lean over and ask for some help. Usually someone ends up just sitting there with a problem putting several hours in to it before it gets solved. Now we could tackle things together which was great.
Setting aside a weekend for developing is a good way to get a lot of things done. So consider this if you feel that team motivation is dropping or that things are just going slowly.