When you fly in a plane and leave the ground on a wet cloud covered day, there is a moment where you break through the clouds, it's as if reality has been hidden from view and then revealed to you. The sun and clear blue sky was there all along, you just couldn't see it.
It would be similar traveling through a long unlit curved tunnel in daytime. There is a point in the tunnel when the light disappears and you can no longer see either the entrance or exit. Maybe the brain starts to think that there is no exit as if the tunnel will go on forever. It can be like this when in the middle of a creative process, or a life challenge. An external image of a curved tube or a broken infinity loop can be a helpful reminder that there is light existing beyond the current position. Light does not stop being a real thing even when the light is not present in our view, it's there outside, above, beyond, entrance and exit. So when we are in the tunnel it's important to do all we can to keep going, even if a little rest is required on the way.