“You must want to enough. Enough to take all the rejections, enough to pay the price of disappointment and discouragement while you are learning. Like any other artist you must learn your craft—then you can add all the genius you like.”

Source: Pages for You

Variations of this quote have been attributed to a number of people, including Eleanor Roosevelt, Samuel Levenson, and Lao Tzu; there is no solid support for any such attribution.
Misattributed

Cited as a piece of anonymous folk-wisdom from the 1940s onwards https://books.google.com/books?id=iNkWAQAAMAAJ&dq=%22Learn+from+the+mistakes+of+others.+You+can%27t+live+long+enough+to+make+them+all+yourself%22&focus=searchwithinvolume&q=%22make+them+all+yourself%22. Not attributed to Eleanor Roosevelt until 2001 https://books.google.com/books?id=ctxi36FCi18C&pg=PA151&dq=%22Learn+from+the+mistakes+of+others%22+%22live+long%22+roosevelt&hl=en&sa=X&ved=0ahUKEwiI_sD5mqDLAhWIKGMKHb8HAZ0Q6AEIHTAA#v=onepage&q=%22Learn%20from%20the%20mistakes%20of%20others%22%20%22live%20long%22%20roosevelt&f=false.
Disputed

Revolution (2014)
Context: Who does a baby think he is before he can recognize his face in a mirror, before he’s taught his name, before he’s drummed into stagnant separation, cordoned off from the infinite oneness? Love is innate. We must be taught to hate, and now we must unlearn it, as the Buddhists say; let it burn, that which needs to burn, let it burn. The class system isn’t fair on them either, poor little sods—packed off to school, weaned on privatized maternity shopped in from a northern spinster. Trying to find love in the tangle of dismantled family. No one can be happy imbibing a poisoned brew. It’s poisonous for us all. They’ll gratefully sigh when we unlock them from their opulent penitentiaries, they’ll be grateful when their fallow lords and empty chambers feed the hungry and house the poor. They know contentment cannot be enjoyed when stolen. They need the Revolution as much as we do. The whole of human history is nothing new, the whole of your personal story is nothing true, you can do with it whatever you want to do—flick a switch, scratch the record off, look behind the veil. Anything you don’t want, discard; anything that hurts, let go. None of it’s real, you know—all that pain, all that regret, all that doubt, not thin enough, not a good enough mum, not a good enough son, not a good enough bum. You are enough; you’re enough; there’s nothing you can buy or try on that’s going to make you any better, because you couldn’t be any better than you are. Drag your past around if you like, an old dead decaying ox of what you think they might’ve thought or what might’ve been if you’d done what you ought. That which needs to burn, let it burn. If the idea doesn’t serve you, let it go. If it separates you from the moment, from others, from yourself, let it go.

Listening Beethoven's F minor Quartet; Quoted by Walter Legge, in Walter Legge: Words and Music (1998) edited by Alan Sanders

Source: Zen and the Art of Motorcycle Maintenance (1974), Ch. 8
Context: I've noticed that people who have never worked with steel have trouble seeing this—that the motorcycle is primarily a mental phenomenon. They associate metal with given shapes—pipes, rods, girders, tools, parts—all of them fixed and inviolable, and think of it as primarily physical. But a person who does machining or foundry work or forge work or welding sees "steel" as having no shape at all. Steel can be any shape you want if you are skilled enough, and any shape but the one you want if you are not.