I think burnout is one of the key challenges that developers face from time to time; luckily it has happened to me only twice, and it hasn't happened in the last 14 months.
I think everyone needs to strike a fine balance b/w work and their personal lives. I'll go a step ahead and say that the later is more important than the former. For me personally, I need to be happy mentally to do anything, let alone work. My relationships with everyone went for a toss when I used to have constant 18 hour days way back in 2014, I thought it was cool to work long and be the guy to beat in the office. How much more wrong could I be? My productivity fell like a pack of cards and I had to realize that I was burned out, and had to take a sabbatical to get back into a good frame of mind again.
The second thing is skipping breakfast; which I, unfortunately, haven't been able to fix so far. There are times when I go till 9.00 PM without a single meal (mentally I would be postponing my meal for the next hour or so, so that I could get a bug fixed or a feature out by then). I used to be so low on energy and have often realized that, had I eaten something, I would've been more productive. Of late, I at least by lunchtime and that's when I begin being productive.
Long story short, don't skip breakfast and don't burn yourselves out. :)