I read years ago via Helen Adams Garrett in "More About Retrogrades" that the German School of Astrology called "Uranian Astro" teaches Retrograde planets have to do with showing us karma and past lifetimes energies we need to work on again. Garrett is part of this school of Astrology and therefore Philosophy, and it makes sense to me as well.
I just opened an older copy of Karmic Astrology "Retrogrades and Reincarnation" Vol 2 pg 14; by the late Martin Schulman in which he indicates the same more or less. Actually, he brings RX planets across as karma being worked on again but does so with explaining "time" and jumping ahead vs living in the moment as in direct motion planets. Rather intriguing to read.
On my mother's 50th Wedding Anniversary, I recall at a party her sister threw for them, she said,
"50 miserable years" in a low voice. Her chart had
Venus rx with Neptune rx - and truly it fit perfectly very deceptive man was my father -, and was miserable in the days when you simply made your bed and slept in it. I was their 1st child and born with Neptune in the 4th house
My daughter has
Venus rx and Saturn rx (her Sun's ruler) and broke up when HE left, with a gigilo type Gemini after 15 yrs. Everyone saw him for what he was, her work mates, her friends, her relatives, everyone but her. She was very much in love for 15 yrs and still is. It sort of wrecked our personal relationship as he hid his personnae behind scapegoating.