"How do you get that inner Zen back where you can focus on personal projects and really enjoy what you do?"

It might be a personal thing.. but the "inner Zen" relies mostly on self confidence, and it is ok not to have it constantly. Especially when approaching new things with lots of unknowns. It is actually cool to experience a discomfort, since it sparkles fresh ideas. But again... sometimes.

Why can't you enjoy your personal projects now? If choosing a "tech stack" is a problem, then choose literally anything that has a live and matching (to you) community around it. You are looking at Rails, and you like what you see, people you talk to (IRC, forums, groups, conferences)? Go for it, and have no fear of missing out on anything.