What if our planet had ten times it's current diameter, and was always darkened by low hanging clouds and perpetually gritty skies?

So thanks to Silhouette for this question—or the inspiration for this question. She asked about what would happen if people still thought the earth was flat. Well, if the horizon were so far away that even the largest things disappeared in the gloom before they sank below the horizon, and if we could never see the sky to note our travel through the cosmos, what would we be like?

How would we think differently? We’d be unable to fly very high due to the grit in the air. We’d essentially be confined to the surface. There would never be any clear days, anyway. There would be enough energy from a close and bright star to penetrate the clouds, but we’d not know it was there.

Would our personalities be different? Technology? Rituals?

I’m not writing a book. This is just for fun.