Since rescuing a street pup on Sunday, everything around me is DOG. As I walked my dog this morning, I found myself becoming alert as we approached another dog (we walk fast). My pup's ears would lift high and she would pull on the leash a bit as the energy between her and the other dog built. As we got very close, both dogs would react to another, sometimes greeting one another with a sniff when they met up. As we began to pull away, my dog might turn her head one last time, but basically, the other dog was out of sight, out of mind. I thought of applying and separating aspects and how they mirrored one dog overtaking another one on the street.
In an applying aspect, the degrees of two planets decrease as the faster planet approaches the slower planet until they are exactly in the same degree either by conjunction, sextile, trine, square, or opposition. In a separating aspect, the degrees between two planets increase as one "flows away" from the conjunction, sextile, trine, square or opposition. Applying aspects tend to be more intense, imminent and anticipatory as they represent energy coming into being - like my dog gaining on another. Separating aspects tend to be more stable and feel as if they are fading. The range for applying is 3° (13° for the Moon) while the range for separating is 1°.
This is helpful to look at when we're considering transits to determine when you will feel the energy at its strongest. You can use it with your natal chart as well. Separating aspects might have been experienced early on, but as you grew, the energy faded. Applying aspects are more likely to be activated throughout life.