"We weren't as similar as we thought," Flajnik toldIn Touch Weekly in a recent interview. "We really did love each other, [but] things just changed."
Robertson, a 28-year-old model from Santa Monica, CA, got engaged to Flajnik, a 29-year-old winemaker from Sonoma, CA, when he selected and proposed to her during The Bachelor's sixteenth-season final Rose Ceremony, which was filmed in November 2011 and aired in March.
But after about 10 months of dating, the couple decided they should take a break, according to Flajnik. The couple came to the conclusion after they spent the weekend in Sonoma together late last month (Robertson had gushed about the weekend on Twitter, posting photos of the pair and how much fun they were having.)
However, a few days into their break, Flajnik and Robertson reportedly decided to "not drag this out" and make their split permanent -- resulting in the pair announcing they had ended their engagement last Friday.
"It was a totally mutual agreement," Flajnik told In Touch.
As for Robertson's Neil Lane diamond engagement ring, Flajnik said his ex-fiancee will most likely have to return it.
"Sometimes they make exceptions," Flajnik told the magazine. "We've been together for 10 months. You have to be together for two years to keep the ring."
In addition to the personal issues the couple had with each other while dating, the public's scrutiny of their relationship apparently didn't help.
"There are always going to be haters. There were so many naysayers, it was really like us against the world," Flajnik explained.