Well, I'll try.. I may have had too much wine to make a particularly good go of it, though

On the one hand (self-evident): a lot of psychology merely hangs labels on things that most people probably already recognise; Maslow's Hierarchy of Needs is a good one, for example, the contents of which would surprise nobody who spent more than five minutes thinking about the issues involved. Cognitive dissonance is the same. More to the point, these labels don't really help anybody or do anything useful. The only value to cognitive dissonance is that it's a name I can use on the internet in threads like this to quickly reference something I agree with; I don't believe, though, that people don't just innately realise that this is the way people work. "Haters gonna hate" does much the same job

I realise these are very basic level examples; my apologies to any reading psychologists who know of genuine uses for giving names to human peccadilloes

On the other side (worthless) are, for example, a series of identified personality disorders (borderline, psychopath, etc etc). I don't doubt that these things exist, but I
do doubt that they exist in isolation, and I doubt that one man's psychopathy is the same as the next. It seems to me that the most that can be said with any degree of certainty is that everybody will fall somewhere along the scale of 0 - 100% for virtually all things that psychologists claim to be able to measure. But can you realistically measure thinking or emotion by one person's analysis of how glib somebody appears to be (for example) on questioning? Is it right to then label somebody as psychopathic/borderline/etc etc because they reach a certain threshold in several areas? Where does that leave individuality?
Sorry, not expressing myself particularly well

May have another go at it after work tomorrow. I should, however, have said in my post, "most psychology that I'm aware of", which is obviously not a great deal. However, what I do know doesn't inspire me to think much of the subject as a whole

I see it as very subjective, and (to be frank) not particularly scientific or useful.