I've been feeling a lot of the tell-tale signs of burnout. I can't stay focused on complex tasks, it feels like I won't ever finish anything, and I keep working when I know I shouldn't.
It's that last one that is most cruel. The worst thing you can do is try to force the work. When you're burned out, there's a litte voice telling you that if you just work for another hour, or open your laptop on Sunday night that you'll have a breakthough and magically just...not feel burned out anymore.
I've been in this situation enough times to know what works for me. Walk away. Step back and think about something else for the weekend. You're smart, and good at what you do, and you'll figure out that problem you are trying to solve. But first, give yourself a break.