Sarah Michelle Gellar is remembering the life of Nicholas Brendon.

After Nicholas died March 20 at the age of 54, his Buffy the Vampire Slayer costar penned a heartfelt goodbye for the late actor.

“‘They’ll never know how tough it is to be the one who isn’t chosen,’” Sarah, 48, captioned a March 21 Instagram post, quoting Nicholas’ character Xander Harris in the show. “‘To live so near to the spotlight, and never step in it. But I know. I see more than anybody realizes, because nobody’s watching me.’”

“I saw you Nicky,” Sarah added alongside a throwback photo of the pair. “I know you are at peace, in that big rocking chair in the sky.”

Her emotional tribute comes one day after Nicholas’ family confirmed his death.

“He passed in his sleep of natural causes,” they said in a statement to The Hollywood Reporter. “Most people know Nicky for his work as an actor and for the characters he brought to life over the years.”