Do you usually spend some of your time learning new programming language/pattern/technology? I mean, I am not the type of person who does same thing over and over again, also like learning new things (I spend a lot of time per month studying new things), trying to get experience and trying new technics, but other side of me thinks that I need to be the best in one of them... My mind flashes blue screen of death sometimes when I am thinking about this...

You need to find the balance between very good at something but never stop learning so you can benefit from other concepts.

Let's say you are a backend dev(I am) it'd be ok if you do not want to learn React but it would be nice if you improve your SQL knowledge or learn more about a provisioning tool or go deeper in software architecture or testing.

You can be a fullstack dev or can be a very strong backend dev.

Try to find the balance. I try everyday.

@cesc1989 yep, I agree. Balance works very well, as you said, since every one choose their path, and I guess I did not realized mine yet.