How to silence the voice that tells you you're being financially irresponsible by spending 4 to 6 years doing a PhD?
When you go to the industry, how do you silence the voice that tells you you could be spending your time advancing the knowledge of humanity, rather than devising new ways to make people look at an internet ad, or helping big stock exchange companies aimlessly move money from account A to account B, without any net gain for the world?