Is It Time to Quit?

The first issue for a student is what to work on. The getting a ph d is all about discovering something new, staking a claim in the intellectual firmament. It's hard to make progress if you don't have the technical tools to solve the problem. If you keep banging your head and not making progress, then there's an opportunity cost. You could have been thinking about something else,. Maybe you would have made progress on that new thing.