It's been a rough week for celebrities in love. First, Taylor Swift and her DJ beau, Calvin Harris, broke up. Then, Gigi Hadid and Zayn Malik split. Now, Demi Lovato and Wilmer Valderrama have called it quits after six years together.Lovato and Valderrama both took to their respective Instagrams last night to mutually announce their separation. "This was an incredibly difficult decision for both of us, but we have realized more than anything that we are better as best friends. We will always be supportive of one another," the pair posted.The couple, having just celebrated a six-year anniversary this past January, began dating when Lovato, now 23, was just 17. Twelve years her senior, Valderrama reportedly had reservations about the age difference at first — but once the duo got together, it was all kinds of #RelationshipGoals, with Lovato publicly thanking Valderrama over the years for loving her curves and helping her maintain her sobriety The pair made their last red-carpet appearance together at this year's Billboard Music Awards, where Lovato used her performance ensemble to make a statement on the importance of gender neutrality