Surah Al-Falaq has a twin! It comes right before Surah An-Nas, and the two of them are always mentioned together. People call them Al-Mu'awwidhatayn, which means "the two that give protection".
Al-Falaq asks Allah to protect you from things outside you — the dark, jealousy, harm. An-Nas asks Allah to protect what is inside you — your heart and your thoughts.
Together they are like a shield for your whole self!