I'm currently a software engineer intern at a security company. The work, while being semi-mundane compared to the projects I'd choose (At least at the level I'm working at), is at a fair enough pace to be fun, and it's aiding my self-development hugely because of the culture at the company.

Overall it's a 40 hour work week along with 3 extra hours of commute a day, so I take to reading mathematics/cs literature on the train and use the rest of my day to either relax or to learn more things.

I would say that while we do have to do what gives us a living, there are options. Contracting, for example.

I should say as well: I also have the same dilemma, I'm interested with everything. So I decided to choose for subjects (such as mathematics) that will give me a better base to learn more subjects.