"Whereas fire rises, air moves horizontally, and earth stands still, water tends to sink and to penetrate."
- Robert Hand (Horoscope Symbols)
People sometimes wonder why the ancient four-element model persists in esoteric and New Age circles, when we have known for centuries that it does not model chemistry. Certainly, if "modeling chemistry" had been its only job, it would have been fired, and we'd only know about it, along with the medical humors, as a footnote.
One reason is that dividing things into fourths is a primal, archetypal response in the human psyche. We're embodied, we move around, we have eyes facing front. This means that almost any time we are active, we are orienting ourselves to front-back, left-right, and sometimes North-South, East-West. Adding up-down-center gives us the magic Seven, but that's another topic.
I don't even like using the term "elements" for them. The Pre-Socratic philosopher Empedocles of Elea used the Greek word meaning root, and in later Latin texts we read "essences," the source of the word "quintesessence" for the "fifth element," Spirit or Aether. I'm going to call them essences from here on.
More specifically, though, the four philosophical essences are a very accurate map of how we experience things. It's very similar to how four taste buds (sweet, sour, salty, and bitter) account for a vast range of taste experiences. Think about a nice day at the beach (since I just had one, and it was very therapeutic). Your experience is dominated by the intensity of four things: sunshine, wind, water, and sand. We know instinctively when they are nicely balanced, and it's a halcyon experience. Walking out in the water to a comfortable depth and just sort of bobbing in place feels wonderful in a primal way. You're being warmed by the Sun, massaged and cleansed by the water, cooled and caressed by the breeze, and supported by the sandy bottom. Swimming or floating has a different feel, as there is less Earth, so it can be even more ecstatic. Returning to the dry sand to sit above the tide line is another way of calibrating the experience: now we are actively "grounding" while still experiencing the sound and smell of the salt waves, the warmth of the Sun, and the cooling breeze.
The ideal time at the beach is nicely balanced, but some days it's too windy, or too hot or cold, or too crowded (so you don't get enough Earth to yourself).
Let's turn the picture inward. Some days you want more Fire, so if you can just sunbathe, it feels great. At other times, you may feel a great need to be in the Water, and experience the flow and the cleansing effect. You may sometimes find a windy day exhilarating, and even enjoy flying a kite. Other times, your ideal experience would be to be buried in the sand, and to let the Earth lend you its stability and reinforcement, while gradually taking away your excesses.
The ancient way of expressing these capacities is called the Temperament, and consists of four Humors: Choleric (Fiery), Sanguine (Airy), Phlegmatic (Watery), and Melancholic (Earthy). In a similar way to how the Essences didn't describe chemistry but still conveyed information about experiences on their level, the old idea that the Humors were identical to four physical fluids maintained in the body turned out to be too simple to explain physiology, but still says something useful about the shape of the Psyche.
Mainstream Psychology has moved on past the humors. Even Jung, when developing his amazing system of psychological types, dismissed the Temperament as "a mere psycho-physical coloration." I don't see what's "mere" about a simple system that shows you how you tend to process experience in your incarnated state!
I found a questionnaire online that does a decent job of assessing what your Temperament at this moment is. There are also ways of deriving your base Temperament from your natal chart. To use the astrological method, you will need to know your birth time as well as date and place. I have had a number of people compare their results from both methods. Most of them were a good match. but some found their current temperament different for various reasons. In my case, the test shows more Phlegmatic than my horoscope does, precisely because I have done inner Alchemy to adjust my overly-dry birth Temperament.
During treatment, I use your Temperament (if known) to adjust the guided imagery, and possibly the choice of gemstones to use. If we don't have the information to start with, I just use intuition to tune the session, and we still come out fine.