Throughout the song, the individual grapples with various challenges, including depression, suicidal ideations, substance abuse, and relationship problems. The diary becomes a means for him to process and cope with these difficulties, providing a safe space to release his emotions.
The lyrics paint a vivid picture of a person at the brink of despair, expressing a sense of isolation, hopelessness, and the need for an outlet to vent their inner anguish. The diary becomes a companion, a confidante, where they can lay bare their innermost thoughts without judgment or fear.
The song also touches upon the theme of duality and the contrast between the person's outward appearance and their internal struggles. The verse, "I smile so hard, my cheeks begin to ache," reflects the facade of happiness that the individual might present to the outside world, while the diary becomes the safe haven where they can acknowledge their true emotions.
Ultimately, "Diary" explores the theme of self-expression, catharsis, and the importance of finding healthy ways to cope with emotional pain and mental health struggles. It highlights the therapeutic power of journaling and personal expression as a means to navigate difficult times.