What is your source of belief in situations like this when the engineering problem is so difficult there's a lot of experts many of whom you admire who have failed in the past yes and a lot of people (experts, journalists, the public) have a lot of doubt about whether it's possible.

Where do you go to both personally intellectually as an engineer as a team like for source of strength needed to sort of persevere through this and to keep going with the project take it to completion.

Elon replied: I mean for me it's simply this this is something that is important to get done and we should just keep doing it or die trying.

I don't need a source of strength so quitting is not even in my nature okay.

I don't care about optimism or pessimism.

F**k that we're gonna get it done.

Impossible Things Achieved by Elon Musk and His Companies

Create a new successful commercial orbital rocket company. SpaceX failed three times to launch an orbital rocket and succeeded on the fourth try.
Create a partially reusable rocket.
Create a new successful car company. Most new car companies go bankrupt.
Create a successful electric car. Previously electric cars had all failed.