Nikki Bella confessed the biggest regret she has in her relationship with John Cena.

In her new book, she revealed all the juiciest details of her life and how "DWTS" has helped her move forward from a breakup. 

Reliving The Pain

In the new book "Incomparable" which she co-wrote with Brie Bella, Nikki Bella went all out and talked about her failed relationship with ex-fiance John Cena

The "Total Divas" star admitted that she had a lot of regrets about her relationship with Cena. However, the biggest thing she wished she had done was to know herself better. 

"I have many regrets about that relationship. The primary one is that I wish I'd known myself better before I got into it. I wish I'd understood how the patterns in my life, and my relationship with my own father, informed how I react to love, boundaries, and feelings of abandonment," Nikki shared. 

Nikki believed that if only she was more open to talking about her feelings back then, she would have saved their relationship. 

"I think I could have averted some of what happened. Because my dad left when I was 15, I learned how to fill in the holes. I expect to be left behind and to find a way to not confront or acknowledge those feelings of loneliness and abandonment," Bella added.

The "Total Bellas" star furthered that she and Cena tried not to be away from each other for too long, but she believed that they did not try enough. 

"Working all of our various side hustle jobs left me feeling almost pathologically lonely," Nikki shared.

In the end, she conceded that their split was partly her fault because she did not know how to say what she wanted. 

"I just didn't know how to identify the emotion. And I certainly didn't know how to ask for what I needed. I was intent on fitting into the contours of my ex's very busy and big life. That was paramount to me, pleasing and keeping him content, not voicing my own needs. He had no idea I wasn't getting what I needed because I never said anything."

Blaming Herself

At some point in her life, Nikki said that she has always blamed herself for her failed relationship with Cena. She explained that she always had that "pleasing bug" where she tries her best to make everyone around her happy. 

And yet in all these, she failed to make herself happy. 

"I am attached to a very disturbing core belief that I am only lovable when I put other people first. That I only deserve their affection because I am useful and handy," Nikki furthered.

Nikki also admitted that John has taught her a lot about life and love. "I learned from my ex that this is a profound fallacy. He could see the real me and love me just the same. It felt too good to be true; I felt undeserving."

Nikki Bella tried so hard to save her relationship with Cena, creating the perfect Nikki and the perfect life for them. Unfortunately, she lost herself and she was unhappy. 

According to Bella, she did not trust John enough with her feelings. 

 "I didn't give him, or our relationship, the benefit of the doubt that maybe it could handle more. Because I assumed he wasn't willing to make sacrifices, I did not persistently ask. Because I was so fixated on what I believed he wanted, I made many decisions on his behalf, even though I was losing myself in the process."

READ MORE: 'Total Bellas': Nikki Bella Breaks BF's Heart With Stunning Change Of Mind