I regret what I have done did a long time ago.

(The title is not at all suitable for this entry. I also can't think of any other suitable title for you entry. Still, any other title like 'My Brother's Wedding anniversary' would do.)

Brother invited some friends to his home for celebrating their webbing ten to celebrate his tenth wedding anniversary. Guests came home are here, but the host disappeared somewhere. (Guests came home, but the host was missing.) The search went on for some time and finally, someone found him at his study. He was drinking all by himself.

His friend Ms Hes asked,"Friend! What is the matter with you? Why don't you do not drink with us? your friends? together. We are supposed to party together on your anniversary. How on earth can you be here here all one? you you alone drink in your study."
　　 Do you know what the host is was thinking of? (Can you tell me what the host was thinking of at that time?)