I slept with a guy next door

my husband was on business trip and I felt so lonely, a guy who lives next door knocked the door asking me if he can borrow the blender, i went to the kitchen to bring it to him, and the next thing was that he was behind me and kissing my neck i couldn't resist  him and i could not take it anymore, so i let my body to decide what's best for me, and we ended doing it in the kitchen floor when he finished, he kissed me on my forehead, and told me he's in love with me, and left i feel i'm really cheap, how come i let myself doing this teribble thing, i'm a married and a decent wife i feel guilty, and feel guiltier whenever i see my husband, i can't look into his eyes p.s.  this thing happened only once, i swear