Yeah! I am to thin!

It finally happened. I am being told I am to thin…ha! I am 5 1” and weigh 119 so its not really true. But, I got pissed at my friend who said it. She, sitting there with her 50 pounds to lose, tells me I am obsessed and need to understand that its not healthy to be so thin. My main question is about my reactive mind/mouth. Why couldnt I just nod and smile instead of getting pissed? I feel there is no thought before my mouth opens and I say something I didnt really need to say. I am one of those speak first think later people. I know I am thinking thoughts which cause this but it feels like I just react without thinking. I have been with you for months and I am not getting any better at it. I am easily irritated and snap at my husband daily. How can I practice not reacting? Every day I promise myself I will do better…and I dont.