For anyone who wants to take the leap but is afraid or unsure, I offer some words that were incredibly helpful for me from some of fantastic friends. To quote my amazing advisor from his response to my "I'm leaving" email:
'We had a Head of Department at Lancaster who used to stomp around the corridors moaning - "I've just lost another student to industry. He's got a great job, has a starting salary bigger than mine, is working on a fabulous project with better resources than we have. In what mad world is this judged as a failure?"'
And another colleague, who's currently a junior professor: 'You know, most Ph.D.ers are smart and successful people. Hence they have a difficulty in saying “This is not for me”. They instead say “I’ve been successful all my life, and I finished everything I started, so I should finish this as well”. By saying that, they choose to hang in there for many years in a depressed state.
Sometimes, the most courageous thing and the best thing to do is to quit when you know you would rather work in another capacity, or when you know you don’t want to work in academia. I congratulate you on your decision and I hope the best for you. ( In case you later decide to come back to academia, it will be waiting for you, so I would not worry about it.)'
Best of luck, those of you that are struggling with the decision. If you're anything like me, if you decide to leave you'll feel better than you have in years =)