When Priscilla Salyers attends Sunday's anniversary ceremony for victims of the 1995 Oklahoma City bombing, she will be thinking how far she has come in fighting depression and survivor's guilt.

She and hundreds of other survivors will bow their heads at the 20th Remembrance Ceremony at the Oklahoma City National Memorial and Museum, marking the day a cargo truck with more than two tons of explosives blew up, killing 168 people.

Salyers plummeted five floors when the fuel-and-fertilizer bomb detonated at the Alfred P. Murrah Federal Building on April 19, 1995.

She remembers the sound, remembers locking eyes with a coworker she would never see alive again and remembers the chaos and noise as the floor disintegrated under her feet. She was trapped in the rubble of the nine-story building for hours, her head beneath a 25-foot column of concrete.

Anti-government militant Timothy McVeigh, who carried out the bombing, and accomplice Terry Nichols were tried and convicted on federal charges. McVeigh was executed, and Nichols received multiple life prison sentences.

Today, the depression does not haunt Salyers as often. The survivor's guilt is not as razor sharp. Helping to design the memorial was a step in her healing.

"I hope we are an inspiration to those who are starting their own journey to healing," Salyers said. "I hope people see that life goes on. So many of us have picked up the pieces and kept moving forward."

Among survivors attending the ceremony will be some of the "miracle babies," six men and women who were aged under 5 and were in the building's daycare center when the bomb exploded.

Despite seared lungs, ravaged faces and mental and psychological scars, they try not to dwell on the past and move on.

One of the daycare babies, Joseph Webb, said he feels like he must share his story to remind the public of what happened that day, but he will not attend on Sunday.

"For me, it's too distracting from the solemnity, the austerity that I want to experience on my own," Webb said.

Former President Bill Clinton, who was in his first term in office when the bombing happened, is scheduled to close the memorial service.

Other officials scheduled to attend are former Oklahoma City Mayor Ron Norick, former Oklahoma Governor Frank Keating, Mayor Mick Cornett and Governor Mary Fallin.

"The lessons learned twenty years ago on April 19, 1995 – and in the months and years thereafter – have changed the way America responds to violence and terrorism," Kari Watkins, executive director of the Oklahoma City National Memorial and Museum, said in a statement.

(Editing by Fiona Ortiz and Mohammad Zargham)