Adele, who on Sunday took home five Grammy Awards, said she had worried her heart-wrenching global megahit "Hello" would be a flop.
Speaking to reporters at the music industry's gala, the English ballad singer said she struggled with writer's block as she took a break from music to raise her son.
In the end, "Hello" won both Record of the Year and Song of the Year. The track appears on "25,' which won Album of the Year.
"I felt the pressure writing '25' very, very much and for a very long time during the process, I didn't really find my voice, and I don't know if I did find it even at the end," she said.
Adele said she feared the 2015 commercial on British television that teased "Hello" would turn out to be "an expensive disaster" and that listeners would not recognize her or care.
In the ubiquitous song, Adele says "hello from the other side" -- as she struggles to reach someone from her past to apologize.
"It's the other side of being a grown-up; it's the other side of my relationship with my friends and my ex-boyfriends," she said.
"I don't know if I lost touch with a lot of my friends because of how famous I got," Adele said, adding that the song also touched on her grandfather, who died 18 years ago.
With Sunday's trophy haul, Adele became the first act to triumph in the three key categories in two separate years.
"25" is the top-selling album of the past decade with the exception of her "21," which achieved the sweep in 2012.