Ryan Seacrest Smiles, Parties With Justin Timberlake at First Event After Julianne Hough Split

USMagazine, Tuesday, March 19, 2013, 9:00am (PDT)

If Ryan Seacrest is upset about his breakup with longtime girlfriend Julianne Hough, he certainly isn't letting on. The American Idol host, TV producer, radio personality, and red carpet star -- known as the hardest-working man in Hollywood -- was as charismatic as always at Justin Timberlake's iHeartRadio album-release show in L.A. on Monday, March 18, just three days after news broke of his split from Hough.

PHOTOS: Ryan and Julianne in happier times

Ever the professional, Seacrest left his personal problems at the door to do what he does best: work. Between songs from Timberlake's new record, The 20/20 Experience, the 38-year-old host chatted with the singer about the inspiration for his new music and his plans for the future.

"Going live with @JTimberlake in less than 10. Come hang, let us show you a few things," he tweeted before the concert. Later, he added, "Pure magic on stage. It was a pleasure @JTimberlake."

PHOTOS: Better after breakup

Seacrest's dedication to his work may be a good thing now, as he tries to take his mind off Hough, but sources say it's at least partly to blame for the couple's split. "It's a lifestyle she couldn't handle anymore," a pal told Us Weekly of the Safe Haven actress, 24. "Work always, always came first [for Ryan]. She wants a more low-key life."

"Dude works all the time," the insider explained. "He never sleeps."

PHOTOS: Julianne's red carpet evolution

Added another source: "Honestly, their schedules were too hectic. It just got to be too much. I think they both just sort of knew they couldn't do it anymore. The travel and lifestyle got to be too much. Who knows if this is just for now, but I think this is for good."

Hough, for her part, is getting by with a little help from her girlfriends, including Vampire Diaries star Nina Dobrev. One day after the breakup went public, the former Dancing With the Stars pro hit the beach with Dobrev and three other pals for a little post-split R&R. The next night, they sat courtside at L.A.'s Staples Center to watch the Lakers play the Sacramento Kings.

This article originally appeared on Usmagazine.com: Ryan Seacrest Smiles, Parties With Justin Timberlake at First Event After Julianne Hough Split