This is the first of what will undoubtedly be many posts on this subject. I'll try to keep each one on the short side. I don't really like reading long blog posts myself, but occasionally they are necessary to elucidate a point.
Astrology from the Classical through the Medieval period was not primarily psychological. As with life, there were pieces of it that one would today certainly label "psychological." That particular term, however, is fairly new, so our astrological forebears would not have used it. There are techniques that identify a person's Primary Motivation, Quality of Soul, etc. Some of these are quite simple, and some are special techniques. But in delineating a chart, it's clear that there are elements that are what we would classify today as psychological.
However, this was not the main focus of a chart, and was not the primary approach to delineation. The modern approach goes something like this: The first house (Ascendant, Rising Sign - they are all synonyms) represents the "mask" that you show to the world, the surface "persona", but it's not the real you. The second house is how you feel about money, and your relationship to it, and all things that support you. The seventh house is your relationship with your spouse, etc.
In Classical/Medieval astrology, the first house is quintessentially you. It is your physical body, your health and your happiness. Much more than a mask that you show to the world, it's the single part of the chart that most represents you as a person with flesh and bone. And the ancients had a far greater respect for the connection between matter and spirit than we do today. Aristotelian philosophy posits that a body doesn't exist without a soul, but that a soul can't exist without a body either. Continuing, the second house is your money, not how you feel about it. It's not your values or what supports you psychologically. It's how much money you have, or how much you have in "movable goods", that is, stuff you could liquidate pretty quickly. The seventh house is your spouse. Not how you feel about her or him, and not the relationship itself. It describes and delineates that other person. And so on through all the houses.
In modern astrology, the houses take on the role of mere psychological extensions of the native. It seems to me that one must have a pretty big ego to think that the rest of the world is an extension of oneself. Based on modern astrological logic, if I cease to exist, then so does everything else. The Medieval approach is that the first house is the native, and that all of the other houses show the world (material and spiritual) that surrounds us.
This is what allows Medieval astrologers to predict, rather than merely psychoanalyze. If a chart shows how you feel about the world, what is there to predict? If, however, the chart represents real things in our lives, and the things that affect us from outside of our own psyches, then we can see what direction those things are headed in, and attempt to predict probable outcomes.