Actress-singer Hilary Duff has opened up about her filing for divorce last month from former New York Islanders center Mike Comrie.

"I don't want to sound bitter because I'm definitely not, but I don't know if people are meant to be together forever," Duff, 27, says in the new issue of Cosmopolitan, being published Tuesday. "Things happen over a long relationship that you can't always fight. A marriage of 20 years, the accomplishment of that must feel really great, but there are also huge sacrifices. I just always want to fight for happiness."

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Duff -- who with Comrie, 34, announced their breakup in January 2014 -- recalled that, "Mike and I were very in love when we met. We both really wanted to get married. I'd been working since the age of 11 or 12, so making that choice at a young age seemed right for me. Maybe it wasn't, but we spent the majority of our time together really happy."

The two wed in August 2010 and have a son, Luca Cruz, born in March 2012.

"It wasn't working well enough to stay together," she told the magazine, "but there was still a lot of love involved. It was just a slow set-in of us not being the match that we used to be. I'm lucky for the person he is and I am, and how we decided to handle this."

Duff co-stars in the TV Land series "Younger," premiering March 31, playing the co-worker of a 40-year-old single mom (Sutton Foster) who gets a makeover to look 26 in order to land a job.

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Comrie, a two-time 30-goal scorer in his 10-season career, played for the Islanders from 2007 to 2009.