Why do I feel this way? my wife kissed another guy while wasted..?

been together 5 years married 1 year and a hlaf, couple weeks ago she kissed another guy when she was wasted, and she came home and told me right away. Since then i have been feeling very insecure about the way she feels about me , when i brought the subject she just tells me to stop going on! She tells me that she is gonna be by my side and would never do it again, but I feel so insecure and that insecurity is making me act in a strange (needy) way. we are both 25. i 100% know she is not cheating and that she is sorry? How do I deal with my feelings to make it work?