I snapped at an old man at the grocery store and now I feel bad

Preface I've had a really bad day. I go to the store to get something I needed for dinner and the line for self checkout is long. Someone announced lane 22 is open and the old man behind me says lane 22 is open to me. I've barely had time to process the original announcement and now I'm feeling rushed. I told him I'm not in a hurry like he is and he can go there. He just gave me a heh heh awkward laugh and went to lane 22. I still finished checking out before him.

I didn't mean to be rude but my patience is gone and I'm just worn out.