What we call a retrograde Planet is a planet whose apparent motion seems to reverse. In reality this phenomenon is an illusion due to the duration of the revolution of the different planets around the Sun in relation to our point of view on the Earth. Sometimes the Earth is faster (than the planets outside its orbit), sometimes it is slower (than the inner planets in its orbit). Only the Sun and the Moon, the 2 luminaires, never regress.
In traditional astrology, the concept of R has been imputed to interiorization and introspection. In karmic astrology a retrograde planet is seen as an “energy node”, that is, an evolutionary constraint inherited from the past that will shape the present incarnation.
Most of the time, planets move in forward motion on, or relatively parallel to, the elliptic, which we can think of as the main highway.
Simply by being contrary to the normal flow, retrograde motion represents an exception to this sense of normalcy. Perhaps it's more appropriate to think of them as seekers or explorers who travel the celestial byways in search of something not available on the main highway.
According to personal researches and in agreement with some famous astrologers, a R planet strongly gets its force from the sign and the house it is rooted in. I see a Retrograde planet as a well. The water is very deep, still in subtle motion, in the heart of the earth. One needs more efforts to extract the water from the well.