The 'Total Divas' star is reportedly devastated about the end of her engagement to the wrestling star, who she has been with for six years.
A source told People magazine: ''He's an incredibly dedicated, driven, ambitious guy. And for the longest time he said he didn't think he had room in his life for a spouse or kids. It seems like in the end that was still the truth ... Now she's heartbroken.''
The pair announced their split in a statement released on Nikki's social media account.
It read: ''While this decision was a difficult one, we continue to have a great deal of love and respect for one another. We ask that you respect our privacy during this time in our lives.''
The split came after John admitted last month that their relationship takes a lot of work.
He explained: ''Relationships are hard. Don't ever think that love is easy. Love is beautiful, but we've had to come to the realisation after being together for five years that love is not easy. We work every day on us. We have our problems just like everybody else. Some of our problems are very public, some of them aren't. But we work every day on us. Anytime I get upset, I always just realise that I can't live without her and I love her and that's why I cave in on a lot of stuff. It takes being able to mesh two lives. I would never ever want Nicole to be in a position where she says, 'I'm holding you back from doing this because I feel it's wrong for us.' And I would never say that to her. That's why she's super busy and sometimes we don't see each other for months at a time, but when we do see each other, it's our time together. I think, for now at least, that is certainly what's making this work.''
His new album Underneath It All is out now.