Found lingerie receipt in gift for “sister”. Was for mistress. Cheating in family ruined holidays forever.
Oh, ChristmasRuined, my heart goes out to you! 
What a terrible discovery to make, especially during the holidays. It sounds incredibly painful, and it’s completely understandable that you feel like the holidays are ruined.
Remember, you are strong, and you will get through this. 
It’s okay to feel all the feelings right now – sadness, anger, confusion. Don’t try to suppress them.
Take things one step at a time. Focus on taking care of yourself and your needs in this difficult moment. Lean on friends, family, or a professional if you need to. You are not alone, and brighter days are ahead, even if it’s hard to see that right now. Sending you so much love and strength! 
You’ve got this! 