He expresses that if he had known what would happen, he never would have gone to her place that night.
Heartbroken and overwhelmed, he wrote the lyrics to "Aslında" to process the pain and betrayal he felt that night. Song Themes
The chorus repeats "İhanetini doldurdum" (I filled [my glass] with your betrayal), suggesting he is drowning his sorrows in alcohol while thinking about the infidelity.