Aaron Hotchner knew that love at first sight did not exist.
The simple truth was, falling in love took time; sharing memories, learning facts, and developing chemistry all contributed to the building of a relationship.
Aaron had learned that lesson with Haley during high school; their dates were at first a casual fling, but soon enough became a rock that he could cling to in order to escape his abusive home.
He had never thought that his feelings with Haley would change; he was a commitment guy, determined to outshine his father's many misdoings by being the best husband and father possible. However, considering his constant absences for work, his marriage eventually fell apart. He still loved Haley at the end, but the truth was that they could no longer make it work. They had been barely holding on even when Jack was born and his cases at the BAU began taking more and more of his time.
Regardless of his disbelief in fairy tale romances, he was sure that an emotional connection could be felt upon meeting someone.
So when he met Emily Prentiss, years after working for her mother, he knew that she was something special.