Nikki Bella has admitted John Cena changed her ''forever'', in a heart-breaking message on what would've been their sixth anniversary.

The pair split up earlier this year when the 34-year-old pro wrestler called off their engagement, but on Thursday (09.08.18) she shared a cryptic post saying she will ''never forget'' her 41-year-old former fiance.

Nikki took to her Instagram to post a picture of an emotional quote, which read: ''You've changed me forever. I'll never forget you''

She added the caption: ''8/9 6 (sic)''

Last month, Nikki admitted her and pro wrestler John's relationship was ''officially'' over, just weeks after she called off their wedding.

She said: ''After I called off the engagement, we tried to work on our relationship to get back to where it was, and in order to move forward with our wedding.

''After much time and soul-searching alone and together, we have decided to officially part ways.

''I had a beautiful and loving six-year relationship with a wonderful man. I have the utmost respect for John, but I know this is what's best for me.''

Earlier this week, John also shared a cryptic post on social media, about vulnerability.

He wrote on Twitter: ''Be vulnerable. It shows you for you. People will judge, disagree, and downright despise. But you will be you.

''Most of those who judge, disagree, or despise do so because they struggle with vulnerability themselves.''

Another tweet read: ''The promises you make mean nothing compared to those you keep. (sic)''

The pair were due to marry on May 5 in California, but they split in April.

Since then, the former couple have been spotted holidaying together but have insisted they are just friends now.