Damn your cock is tiny!

A tiny dick and a hot partner.... This is how the story goes.
We all know sex is important! If you are a man with little or no future, a loser? She will break up with you and find someone with a future. Having experienced a pathetic small penis, you can be sure her new man/men will be at least average in size but more likely large.
IF, you are one with a future, she may because of the security, stay with you.
However, she will eventually give in to her inner desire of being fucked properly and once she has, well........... YOU, are fucked!
You can shake your head and say never, you can convince yourself that you know her well and she would never!
Women are masters when it comes to cheating, having affairs.
It's not a character flaw, it is biological, a genetical program, at it's strongest when she is ovulating.
There is a way where everyone is happy and that is to let nature do its thing; wife sharing, hotwifing, cuckoldry. Basically, she gets that good sex she needs with the love and support of her partner.