I think my square compositions got better when I stopped thinking about it. I let my instinct tell me if something looks good.
I have talked with others who said they shoot with the intention of cropping in the darkroom. I'm a full frame square print kind of guy.
As for landscape shooting, I have never really been a grand sweeping landscape guy. I like to pick out pieces of the landscape that fit into the format I am shooting at the time. Maybe the square is not natural but it can be used to the photographer's advantage if they let it.