You Can't Want Both

Enchiridion by Epictetus, Chapter 13:

For be assured, it is not easy at once to keep your will in harmony with nature and to secure externals; but while you are absorbed in the one, you must of necessity neglect the other.

The Internet Encyclopedia of Philosophy defines "external" in the context of Epictetus's philosophy as:

‘external’; any of those things that fall outside the preserve of one’s prohairesis, including health, wealth, sickness, life, death, pain – what Epictetus calls aprohaireta, which are not in our power, the ‘indifferent‘ things.

The Epictetus quote, and particularly the last sentence, reminded me of a passage in The Fountainhead:

“Can’t you be human for once in your life?”
“Human! Simple. Natural.”
“But I am.”
“Can’t you ever relax?”
Roark smiled, because he was sitting on the window sill, leaning sloppily against the wall, his long legs hanging loosely, the cigarette held without pressure between limp fingers.
“That’s not what I mean!” said Keating. “Why can’t you go out for a drink with me?”
“What for?”
“Do you always have to have a purpose? Do you always have to be so damn serious? Can’t you ever do things without reason, just like everybody else? You’re so serious, so old. Everything’s important with you, everything’s great, significant in some way, every minute, even when you keep still. Can’t you ever be comfortable—and unimportant?”
“Don’t you get tired of the heroic?”
“What’s heroic about me?”
“Nothing. Everything. I don’t know. It’s not what you do. It’s what you make people feel around you.”
“The un-normal. The strain. When I’m with you—it’s always like a choice. Between you—and the rest of the world. I don’t want that kind of a choice. I don’t want to be an outsider. I want to belong. There’s so much in the world that’s simple and pleasant. It’s not all fighting and renunciation. It is—with you.”
“What have I ever renounced?”
“Oh, you’ll never renounce anything! You’d walk over corpses for what you want. But it’s what you’ve renounced by never wanting it.”
“That’s because you can’t want both.”
“Both what?”
“Look, Peter. I’ve never told you any of those things about me. What makes you see them? I’ve never asked you to make a choice between me and anything else. What makes you feel that there is a choice involved? What makes you uncomfortable when you feel that—since you’re so sure I’m wrong?”

Keating wants the "simple and pleasant" externals of the world and builds his life around that. Roark wants to achieve his own goals and values according to his own standards. These are incompatible goals.