We were up against our biggest competitor of the season, and I was certain. Close the letter with a polite and professional conclusion, such as "Yours sincerely" or "Best regards. Close the letter with a polite and professional conclusion, such as "Yours sincerely" or "Best regards. I have been on the swim team since I was a little girl. . " Sign your name below the closing, and consider. " Sign your name below the closing, and consider.