Are all the psychological issues out there really just a byproduct of miserability?

generally speaking, you are kinda in the right ballpark in your generalizations, almost, kinda. True, seizing "control" of your life/environment is a good thing, and true, finding happiness/peace of mind is equally desirable, but sadly, no, all life's "BS" will not suddenly disappear, it just becomes more manageable is all. And yes, misery will bring about lots of BS--or lots of BS will bring about misery, hard to tell which brings which or if they each bring the other. No matter, if we can avoid stepping in bullpoop, we would all be better off--it's just that sometimes we cannot avoid stepping in the poop, mostly because we cannot always see where it lies.