I've actually been thinking about this a bunch the last couple of months and it's a truly painful dilemna!
At a high level, for those of us who code outside of work, we're constantly faced with the choice of either working on something that we find interesting vs. something that would further our careers. It's awesome when they align, but it can be painful when they don't.
I sometimes feel guilty when I choose to work on passion projects... but if I instead choose work on professional development, I feel like my creative soul starts to wither a bit.