I've felt this way too in the past but gradually realized that's it OK not to know everything. Specialize in one area, make it your 'home base', and then test the waters of other tech from there. Once you find something new that you like you can gradually chip away at it and expand your skill set. I've got several things on my radar right now, but still put my specialty first. With this state of mind, I don't feel overwhelmed, but still have lots to look forward to.