It also means not a good time to start new things connected to the planet and sign and house in your chart, more of a time to go over, review, relook at some of the things that happened in connection with the planet/sign/house. Other obstacles or conflicting energies can prevents the forward movement of the planetary energy.
The most notorious one that people seem to notice in their day to day affairs is mercury. Not a lot is said about any of the others.
The outer planets, Uranus, Neptune, and Pluto as well as the Moon's nodes, spend a great deal of time retrograde and the effect is not that noticable in day to day affairs. Many astrologers say when the outer planets are retrograde the energy turns inward, a time of looking at who and what you are, and reflecting on what changes need to take place internally.
Hope this helps.
moondust