I believe Feynman is saying stay focused on your work, don't get too caught up changing things or keeping up because of other shiny things, you may miss important innovative ideas on your own work. It doesn't mean ignore others work but sometimes it is better to work it through yourself for understanding and then compare. Put all the energy into your work first and foremost. Same could go with starting a company or p…
It can also be the opinion of others. A lot of people, especially when you're doing something that goes out of the ordinary, will judge you for not researching more conventional things. You end up trimming your research so that it pleases people more.