The reason for this apparent retrograde movement of planets varies. Superior planets, Mars, Jupiter and Saturn are retrograde when they are in signs opposite to the Sun, in other words, when they are just ahead of the earth and we are trying to catch up with them until such time when they are a bit behind the earth in the ever going orbital race. The remaining time they are in direct motion. Many views exist on the astrological implications of such apparently retrograde phases of planetary motion. Most astrologers agree that at least subtly different effects are produced by the same planet when it is in direct in contrast to retrograde motion.
Some astrologers tend to put too much emphasis on the retrogression phenomenon.
Nothing more elaborate is generally made of the phenomenon of retrogression in most classics. Those with retrograde planets often respond to 'time' in a nonstandard way. The concept of karma generally is considered to be associated with linear time. This in itself is neither good nor bad. Some believe that retrograde planets only manifest strongly in the lives of those who have advanced sufficiently on the spiritual path and have the heightened inner capability and sensitivity to perceive and express the energies that the retrograde planets represent.