One of the great things about using different languages on my off time is that the number of things that fit my brain has grown over time. It doesn't actually take that long for an experienced polyglot programmer to pick up a new language.
I think use what fits your brain is the kind of advice that sounds good but does most people a disservice. At work use what allows you to ship high quality code, on time, within the business constraints that you have. But you'll have much better options in your career if you take at least some time to expand your brain so more things fit in it.
I guess what I meant by "use what fits your brain" is more along the lines of, "try a bunch of languages first, then use the one you like most". Without experimenting, you'll most likely be lulled into thinking your first language is the one that fits your brain best. I would disagree with the notion that a language fits one's brain after you've picked it up. I really don't like javascript, for instance, and I've used it quite a bit.
I think use what fits your brain is the kind of advice that sounds good but does most people a disservice. At work use what allows you to ship high quality code, on time, within the business constraints that you have. But you'll have much better options in your career if you take at least some time to expand your brain so more things fit in it.