Answer by taking a quote from the following article:

"My Happiness" is a song by Australian rock band Powderfinger. It was released on record label Universal Music Australia on 21 August 2000 as the first single from the band's fourth album, Odyssey Number Five. The single is Powderfinger's most successful; it peaked at number four on the Australian ARIA Singles Chart, and charted in the United States on the Hot Modern Rock Tracks chart--the first Powderfinger song to do so. Powderfinger frontman Bernard Fanning wrote the lyrics for "My Happiness" as a reflection on the time the band spent touring to promote their work, and the loneliness that came as a result.

"My Happiness" was put on heavy rotation by Los Angeles radio station KROQ-FM two months prior to its United States release, and Powderfinger signed a contract with United States label Republic as a result of the song's early success. Beat journalist Jayson Argall joked the song had received "a bit" of airplay. Although "My Happiness" was subsequently dropped from KROQ's roster, other radio stations continued to give the song high priority. "My Happiness" peaked at number 23 on the Hot Modern Rock Tracks, making it the first Powderfinger song to appear on a Billboard chart. According to Susan Groves of WHRL, part of the song's success came about because very few people knew of Powderfinger, but were drawn towards "My Happiness" because it was "melodic, [and] pretty"--a change from what she described as "middle of the road rock" popular in the United States. Meanwhile, Australians were "starting to get sick of My Happiness"--Cameron Adams argued in The Hobart Mercury that this was one of the reasons Powderfinger decided to focus on the offshore market. Powderfinger performed "My Happiness" live on the Late Show with David Letterman while touring North America with British rock group Coldplay. They were the fourth Australian act (after The Living End, Silverchair, and Nick Cave) to play on the show. The band also did free promotional shows leading up to the release of the single. In Europe, "My Happiness" received approximately four weeks of airplay on German music video program Viva II, and the band sold out for three nights in a row in London, partly due to the success of the single.

How did they promote themselves?
The band also did free promotional shows leading up to the release of the single.