She told Billboard.com songs "U Want Me 2" and "Don't Give Up on Us," which appear on her upcoming greatest hits album "Closer: The Best of Sarah McLachlan," reflect her heartache.
"I'm separating from my husband, so these are the songs about that," said McLachlan, 40, who lives in Vancouver, British Columbia.
She and her husband, band drummer Ashwin Sood, have two daughters, 6-year-old India Ann Sushil and 14-month-old Taja Summer.
McLachlan called the situation with her husband "pretty gross," but did not explain reasons for the separation or if she thought it would lead to a divorce.
She described "U Want Me 2" as "about that really uncertain, confusing place at the end of a relationship, when there's no communication or closure, everything's still up in the air and there's a lot of anger and sadness. It's sort of that working through 'How do we move forward ... with some dignity and grace."
She said "Don't Give Up" was "pretty self-explanatory, basically just a plea to give it another chance and keep trying."
McLachlan wrote both songs with producer Pierre Marchand of Montreal, who has produced all her albums since "Solace" (1991). The video for "U Want Me 2" premiered on Amazon.com Wednesday.
"Closer" will be released Oct. 7 on Arista Records.
Duggar sisters unveil Christian dating rules in new book
McPhee, Cokas 'working on their marriage' after affair