So the sadness that accompanied working a min wage job full time evenings and weekends through 6 years of university was my inability to pick and maintain my goals, not economic stress and lack of sleep. I feel so daft.
It was a clear signal from your subconsciousness that you were putting time and effort in something that didn't bring long-term value. If we lived in a pre-corporate era, you could have considered a trade, or helping run a small business, building rapport with the owner, or something else that would have had more meaning. Such things build up character, you sort of gain velocity and habits that help you propel yourself further later in life.
Except we destroyed that with low interest rates and turning a blind eye for anticompetitive behavior. Now most people are replaceable cogs that ran out of goals that would motivate them. That's the real, and very big problem.
I hope the degree was worth it, because otherwise you have wasted 6 years of your life. Paying for some administrators' trips to Hawaii with your student debt. And that depression feeling was a very clear early warning that could have helped you prevent that.