I feel this a lot too, but I find that I can quell the anxiety by looking at the huge list of $things_i_dont_know not as a chronicle of how far behind the curve I am, but instead as a buffet of new techniques/technologies that I can sample. Many will be irrelevant to the things I'm building, but some will likely help improve my productivity or ease my maintenance burden.
So I try to have a taste of one or two new things every so often; try them out on a couple of projects to see if they help me, or if they just confuse and overcomplicate. I'll never be able to try them all, but I feel like I slowly get a better understanding of many of the new items, and feel a bit better about ignoring things that I've already established aren't likely to help me to be more productive.
So I try to have a taste of one or two new things every so often; try them out on a couple of projects to see if they help me, or if they just confuse and overcomplicate. I'll never be able to try them all, but I feel like I slowly get a better understanding of many of the new items, and feel a bit better about ignoring things that I've already established aren't likely to help me to be more productive.