Failed again again and again

Today was my first day of the third or fourth fast that I started this week and I blew it again. My husband's son came over and we had pizza. It's really hard for me to say no to social occasions but especially to hunger. But tommorow nothing will stop me, I'm really determined. I don't remember who wrote on this forum that when we fail we learn a bit more about ourselves and our bodies. I really think that I can make it this time but please be supportive.