Today is the first day of the end of my marriage

Tomorrow Jessica is going to go away for the weekend with a man called James who she met on loopy love - an internet dating site. I tried begging her not to but she says that her life is boring, that she only lives to serve her kids, that she wants some excitement. If I stop her from going - I threatened to tell the soon-to-be-lover's wife - she will be unhappy for ever and the subtext is that she will hate me accordingly. I have no options. I tried rage but she pointed out that I had affairs before I married her. I tried to offer to make things better but they cannot be better than the thought of her weekend away. I threatened to lock her out on her return and leave her clothes in the garden in bin bags but she knows I dare not risk losing my kids and becoming one of those sad men you meet in parks and cinemas on Sundays. So, I am beaten down. My options few as they were look increasingly unattractive. I am bereft today.