Many people here might be in a similar situation to me, but I took an online masters program that allowed for continuing education following completion of the degree. This has become one of my hobbies; I can take classes at my own expense, not worry about my grades, and just enjoy learning. I can push myself as much as I want and since the classes are hard, just completing 1 assignment is enough to force me to "think". Just sharing my experience for people who might be looking for ways to challenge themselves intellectually.