Men don't grow on trees and close friends are bound to snatch them from within the same circles.
But the phenomenon of what many call ukushaya ngestina is every lover's worst nightmare. And it knows no age.
Istina is very dangerous. It has ignited generational wars, families have become enemies and lives have been lost because of it.
But why is istina so unforgivable?
Relationship expert Sharon Theron says people feel istina is a betrayal of the highest order.
"All victims of istina are close to the perpetrator, which makes for a very sour taste in the mouth of the victim."
Theron says istina does more than just hurt the partners. It could hurt the whole family, especially if there are kids in the picture.
This is evident in *Andile's case.
The 29-year-old TV producer says she betrayed her lover of five years after she fell in love with his close cousin.
"There was always this electricity between me and *John. He seemed to be more caring than his cousin. Every time I visited he would be the one cooking and taking care of me while John was out drinking.
"Things got out of control one day and we ended up kissing. We declared our love for each other. For two years we dated without anyone knowing until he caught us in bed together when we thought he would come late as usual. He didn't say a thing and just left."
Andile says the next day her boyfriend came over with his friends, who beat the hell out of John.
"Though I am now married to John I can't freely visit his family because they are close to my ex."
Carol Williams, a psychology student at Medunsa, says people get a thrill from taking something that does not belong to them. She says that because istina is forbidden fruit, it tastes sweeter, but she warns that it can have extremely dangerous consequences.
"Istina destroys trust and it leaves people feeling vulnerable. It is very painful for the person on the receiving end to deal with it because it raises many questions."
*Nomsa, 36, a cashier at Spar in Honeydew, is testimony to Williams' notion.
She says the hatred she has for her former friend of 20 years who "stole" the father of her three-year-old daughter from her is so deep that she does not see any closure to the issue - ever.
Nomsa discovered the relationship between the father of her child and her friend when she saw a love SMS from her best friend on her lover's phone.
"At first I thought I was hallucinating. When I asked my ex about the SMS he broke down and cried. He confessed that he had been having an affair with my friend for years. I felt very betrayed because I never expected this from my best friend."
Nomsa says she had known her friend since they were both in primary school.
"We shared almost everything. She knew all my secrets and I knew hers. Whenever I had problems in my relationship I shared them with her. I was so stupid."
Williams says because the friend usually knows the ins and outs of the relationship it leaves the victim feeling helpless. Often the victim feels that the friend capitalised on her weaknesses to win the lover's heart.
*Zinzi is another betrayed friend whose husband of 10 years divorced her for her best friend.
"I loved both my friend and my ex-husband with every beat of my heart. I had two kids with my ex. I used to ask my friend to cook and take care of my man when I was away. That is how much I trusted her."
Zinzi says she was shocked when her man filed for divorce after a petty fight.
"During the argument he compared my behaviour with that of my friend. He then dropped the bombshell and told me that he was in love with her. I nearly killed both of them."
She says she saw a few signs but overlooked them because she loved and respected both her ex- husband and her friend.
"My friend used to ask a lot of questions about my man. Things like 'what did you do on your date?' and she acted shy when he was around or giggled at every word he said.
"He would stop holding my hand and didn't seem to pay as much attention to me.
"He used to ask questions about my friend's relationship. I was suspicious but I didn't want to blow things out of proportion."
But *Asanda, who confesses she stole a friend's boyfriend, says those involved in istina should not be condemned. She pleads love and scarcity of males.
"Men don't grow on trees."
* Not their real names