There were a few personal anecodes some pages back, mine among them.
To expand on my own story a little: I went into the first few fields of study for a combination of reasons, including that I was capable of them, that I perceived family expectations as valuing certain fields of study over others, and that I found them interesting to learn about to varying degrees. It turns out, however, that while it is possible to engage in tertiary or above studies with these kinds of motivations and conditions, it is more difficult to maintain motivation -- or to move toward some level of career satisfaction -- without more powerful motivational elements. At least for me.
I also have four degrees (and parts of another--five different kinds), in four (or five) different fields of study. While I work formally only in the last of these fields, I firmly believe that the others enriched my life experience, and contribute to my understanding of others' perspectives, and my capacity to problem-solve creatively.
Understanding your own behavior is a perfectly legitimate reason to have undertaken studies in psychology. Now that it appears you are finding your interest in the field is restricted mainly to understanding yourself, rather than other people, you have obtained what you needed from this stage of your education and whole-person development.
I think another way of framing what you are calling "overstudying" is that you, along with most GT adults, are likely to be a lifelong learner. Some of the topics you pick up to learn may turn out (intentionally or not) to be relevant to the work which pays your rent and puts food on your table, and is identified as "contributing". Some of it may be purely to feed your own thirst for intellectual growth. Neither is more worthy than the other.
And finally, you have value simply because you are. A unique, precious human being--a singularity in history, never to be repeated again. That is enough.
