A lifeboat drill that was supposed to take place the day of the sinking was canceled by the ship's captain.
According to a survivor's testimony, it was completely out of the ordinary for a Sunday to pass without a lifeboat drill. April 14, 1912, was the last Sunday the Titanic would ever see, and the day of the sinking (technically, the Titanic sank on April 15 at 2 a.m.).
It's unclear why the drill never happened, and if it would have helped with getting people onto to the boats, but it definitely wouldn't have hurt.