Lupita Nyong’o, who played opposite Chadwick Boseman in blockbuster Black Panther, took to social media Tuesday to mourn her friend, the first time she’s spoken publicly about Boseman since his death in late August from cancer.

Writing from a place of “hopelessness” to describe a man who “had great hope,” Nyong’o, 37, said Boseman’s untimely passing has been a gut punch “every morning.”

“I am aware that we are all mortal, but you come across some people in life that possess an immortal energy, that seem like they have existed before, that are exactly where they are supposed to always be—here! … that seem ageless,” Nyong’o wrote. “Chadwick was one of those people.”

“…I remember being struck by his quiet, powerful presence. He had no airs about him,” she continued, “but there was a higher frequency that he seemed to operate from.”

“I think he understood the power of words and chose to manifest power through his word,” she wrote. “He used his mouth to build, to edify, never to break. And he used it to tell some regrettably lame dad jokes.”

Boseman inspired Nyong’o to be “better, less petty, more purposeful” without him “imposing himself or his ideals on others. And yet he also made damn sure that his life meant something,” she continued. “He was unwavering about that. He cared so deeply about humanity, about Black people, about his people. He activated our pride.”

Nyong’o concluded her statement by encouraging people to cherish every moment. She ended by saying “I promise not to waste my time. I hope you will do the same.”