This topic is really interesting to me, and I can see both sides and I guess it really does depend on what you are doing as well.
One of my goals at the moment is working on my resilience. To be passionate about what I do, but not overly.. emotional (i.e. don't let things get to me to the point where it starts to get distressing). The key I've been told is to stay passionate, but objective, but at any point still be able to walk away. It's when you start taking everything to heart, fighting every battle, and becoming more brittle to change that it can start to have a negative influence, both on your health and on your work.
I guess the thing here is that emotion and being emotional have very strong connotations, but they are slightly different. You can put emotion into things, but when it gets emotional is when you need to step back and go, hey, why is this happening. If it is a positive thing i.e. you are over the moon about something, that's fine but if it is something like, someone has criticized your work and it really hit a nerve, that's when you need to think of the root cause.