I don't worry about it too much. I'm a generalist, but I don't try to know everything. I spend a little time learning what interests me (currently Haskell and Parrot PIR), and a little time learning what I need to for work (currently Catalyst). I'm usually interested in the stuff that I need for work, so that works out nicely.
When something new and shiny comes my way, I play with it for a little bit to see if I'm interested. If so, I study it more. Otherwise, I don't. Parrot passed that test for me, PowerShell didn't.
It's no fun chasing knowledge you feel obligated to learn. The whole point of the path I've chosen is to enjoy what I'm doing and to learn how I can enjoy it more with different tools.