Don't ever sum up Fours as representing and needing structure and stability. The geometry of the square gives them that association and rightfully so.

However, here's another perspective on Fours. Geometry shows us that by adding that fourth point above an equilateral triangle we make the leap into the third dimension of length, width and height with the formation of the tetrahedron, the first Platonic solid. The tetrahedron is associated with the element of fire yet is a stable pyramid made up of four triangles. Within the stable structure they create around themselves they burn brightly with new visions of self.

Fours explore these principles through:

Hearts - Relationship and love
Clubs - Knowledge and understanding
Diamonds - Sense of identity and values
Spades - Sense of accomplishment