Chris Sullivan on Kate and Toby's 'This Is Us' Ending: 'Nothing Is Meant to Last Forever'

Chris Sullivan has come to terms with the end of KaToby.

The This Is Us star spoke to Entertainment Weekly about the 100th episode of the NBC series, which aired on Tuesday night. In it, Kate (Chrissy Metz) and Toby (Sullivan) officially signed divorce papers after months of struggling to make their marriage work — ending their relationship for good.

While some fans were heartbroken by the split, Sullivan said he ultimately understood why it was important to show the downfall of his character's relationship.

"This show addresses every aspect of human relationships, and that includes the ending of relationships," Sullivan, 41, said. "So it's been an honor to take on this portion of the storytelling. Dan [Fogelman, the show's creator] and the writers have done what they always do, which is even when things are hard, even when things are painful, they treat the characters with compassion and respect, and they treat the audience with compassion and respect. And as painful as it has been, it has made it a beautiful experience."

Sullivan and Metz, 41, have been vocal about the emotions involved in filming the split — with Metz even posting on Instagram that she felt "physically ill" while filming the 100th episode. Despite the real emotion, Sullivan reminded readers that sometimes, things don't last.

He added that saying goodbye to Kate and Toby's marriage during the show's final season started the send-off of his time on This Is Us — but it also leaves a greater takeaway.

"The thing I keep wanting to say and wanting people to hear is: Nothing is meant to last forever, including this show," he said. "But we are meant to take away lessons from every life experience, including this show."

"So this show has taught people about themselves, about what they do well, what they need to improve," he continued. "And I hope people are asking themselves, where do I go from here? This show has taught me a lot. What now? So I hope that's where we end up."

Sullivan added a bit about Kate and Toby's connection, too, and how it may forwarn real-life relationships. "It is possible for people to love each other and for them to not be a good couple," he said. "It's possible for people to be a couple and not love each other. The thing with Toby and Kate is, it should be a canary in the coal mine for people to process and treat and navigate their traumas before they get into a relationship."

This Is Us will continue airing at 9 p.m. ET Tuesday nights on NBC until the series finale on May 24.