I agree with that. You need a side project that makes you feel you're the boss. You will decide what to do, no pressures, no strict due dates and even no due dates :) Finish it whenever you want or don't finish it, no problem.

When I'm close to the another burnout syndrome, that is the cure for me. I say, "screw it, let's do something fun." You can try different colors, shapes, fonts and find mates to do it together.

You don't have to publish a serious product. Do it for fun, not for money, not for your boss.

Make a calender,print and hang it on the wall. Look how he is happy with that. Design a toy in 3D and print it with 3d printer and put it on your table as he did

You can just play around. And that is exactly when you learn the most.

This pretty much sums it up.