Very interesting and I completely agree with the bits about being stuck and analogies to physical exercise. One struggles to climb the stairs, another struggles to finish a marathon. Both are just people at the edge of their respective, current levels of fitness. But one has reached further out because, when hit with the struggle of climbing the stairs, they didn't take it as evidence that, "I'm just not an exercise person" then go to pieces and quit. Well, maybe they did, but they picked themselves back up and returned to the stairs over and over until climbing stairs was no longer the edge of their fitness. Eventually, stairs became marathons.
As for Bertrand Russell, he did do lots of maths while doing philosophy of maths, and also knew a thing or two about being stuck. He wrote that he would sit down at his desk after breakfast with a blank piece of paper before him. By supper, the page remained blank. I believe this was while trying to find a way out of his paradox.