“We have to serve ourselves for many years before we gain our own confidence.”

But somehow they manage to summon up enough self-belief to overcome the self-doubt, which enables them to back their creativity. The Beatles were just a bunch of young lads with time on their hands who found the confidence to persuade themselves and then the world that they were musicians.
Think Like an Artist (2015)

Nobel lecture (1970)
Context: We, holding Art in our hands, confidently consider ourselves to be its masters; boldly we direct it, we renew, reform and manifest it; we sell it for money, use it to please those in power; turn to it at one moment for amusement — right down to popular songs and night-clubs, and at another — grabbing the nearest weapon, cork or cudgel — for the passing needs of politics and for narrow-minded social ends. But art is not defiled by our efforts, neither does it thereby depart from its true nature, but on each occasion and in each application it gives to us a part of its secret inner light.

Source: Indian Opinion (1 October 1903)

Source: The Remains of the Day

Revolution in Laos: Practice and Prospects (1981) (excerpts)

"Carmel Point"
Context: Now the spoiler has come: does it care?
Not faintly. It has all time. It knows the people are a tide
That swells and in time will ebb, and all
Their works dissolve. Meanwhile the image of the pristine beauty
Lives in the very grain of the granite,
Safe as the endless ocean that climbs our cliff. — As for us:
We must uncenter our minds from ourselves;
We must unhumanize our views a little, and become confident
As the rock and ocean that we were made from.

The Fourth Nelson Mandela Annual Lecture Address, Johannesburg, South Africa https://www.nelsonmandela.org/news/entry/the-fourth-nelson-mandela-annual-lecture-address (29 July 2006)

1940s, Fourth inaugural address (1945)