Nikki Bella gets cold feet once again about marrying John Cena

Cast member John Cena (L) and Nikki Bella attend the premiere of "Blockers" in Los Angeles, California, U.S. April 3, 2018. REUTERS/Phil McCarten - RC1DBF93F9A0

Nikki Bella is opening up about her decision not to marry John Cena.

In a sneak peek of the season finale of "Total Bellas," which airs Sunday, July 29, at 9 p.m.  on E!, the 34-year-old WWE star explains her rationale to her twin sister, Brie Bella, and their mother, Kathy Colace.

“It’s tough because he’s, like, fighting really hard for me. And that makes it really tough,” she tells her family members while in the car. “... There’s something that’s making me not, like, feel like I can walk down the aisle right now. That doesn’t mean never with him, I just can’t do it right now.”

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The reality star goes on to explain that, for the first time, John appears to be “all in” when it comes to their relationship and is ready to work on whatever's necessary. Nikki, meanwhile, feels that she needs to focus on herself for once.

“We naturally just give and sacrifice and I’ve been doing it for a long time,” Nikki says. “I was at the point, like, if I don’t pack up and leave now, I know my personality, and I’m just going to again put myself on the back burner, so I legit have not slept. I packed until four in the morning.”

This isn’t the only time the wedding has been called off. The first time it was cancelled due largely to John’s hesitation about having kids. But, as Nikki tells Brie and Kathy, she “got so excited” when John, 41, told her he’d changed his mind about being a dad that she “didn’t give myself long enough” before jumping back into an engagement.

“I couldn’t believe it. I never thought I’d hear that,” she says. “But I realized there were just such deeper problems. And I don’t want to be the 66-year-old woman who starts living her happy life at 63. I don’t want to be that.”

When Brie asks if this is it for their relationship, Nikki doesn’t seem too sure.

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“He wants me to take the day to really think about it, but to have a healthy, happy lifetime with him I have to take a while to myself,” she says.

In the confessional, Nikki goes on to explain that a lot of her hesitation simply comes from pressure and required timelines.

“John, when I left, he wanted to me to give him a few days to make my decision,” she reveals. “This has been my issue the whole time. It’s a pressure thing. Everything is a time limit. Like, we have to get married [at] this point, and you have to do this. Nothing can just be.”

Nikki continues, “So it’s like, even when he gives me this time limit to make a decision, if I’ll get married or not, it’s just like, I can’t even tell you. You can’t put a time limit on it. You just can’t.”

In a previously released clip for this week’s finale, Brie tells Nikki that John “lost the woman of his dreams.”

Since calling off their engagement in April, John and Nikki have had their fair share of ups and downs. Despite a rumored reconciliation in May, Nikki recently confirmed that the on-again, off-again pair are currently “just friends.”

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“He is not only my best friend, but he truly is one of the best people I have ever met, and he has patience with me and he has really taught me a lot over the last few months, and I think one of those things is an inner strength that I thought I had, but didn't realize how strong I had it,” she said in a vlog earlier this month. “... Hopefully one day we will get back together. And if we don't, we just want each other to be very, very happy.”

In her vlog, Nikki also commented on the "Total Bellas" season finale, calling the episode "very honest and raw and real,” before telling fans that they’ll “see why John and I are at where we’re at today."