A man stands on a pinnacle holding his arms up to the sky in a gesture of delight and well-being. Pentacles form an arc from one hand to the others and in the middle is the moon. The astrological attribution is Moon in Taurus and the title is Success. The position of the man's arms is similar to the horns of the Taurus glyph.
The Moon has to do with change and changeableness. It is not a robust energy and likes to be sheltered from the stress and strain of life. In modern terms it has to do with the inner life and the unconscious. The Moon is exalted in the fixed earth sign Taurus. I imagine the Moon feels safe there, and because she is concerned with feelings, desire, and the inner life feels at home with sensual Taurus.
The moon is a fast moving planet, going through the whole zodiac every month, and also changes her form every few days in a cycle. Because of this her primary attribute is change. If it weren't for kabbalah this card might have been called "The Lord of Temporary Success".
The Six of Pentacles, like all the Sixes, is in the sphere of Tipareth and somehow this very positive (and solar?) influence mitigates the changeableness of the Moon and we are left with "Success". A very positive card.
The man looks conscious of his success, and happy about it but I don't see anything gloating or defensive in his attitude. His arms are wide leaving his chest open.
Lon Milo Duquette says that in a reading this card can help the surrounding cards manifest their qualities in material reality. He was referring to the Thoth Tarot but I don't see why it wouldn't be the same in the Cosmic Tarot where at least the Minor Arcana is largely based on the Thoth.