When you experience an attraction to another person, your body is dumping dopamine into your system and you experience that dopamine as romantic love. Emotions are not abstract metaphysical experiences, they always have a material world element inside your body. In all seriousness, emotions are physical things.
If your are experiencing that emotion for someone who is your spouse and they experience something similar for you back, then it’s a pleasant and positive experience for you both. Assuming the relationship is functional, productive and happy, it’s quite logical to allow the emotions to continue and encourage them.
However if these emotions develop inside you for someone outside the relationship, things can quickly escalate toward dramatic outcomes. Dopamine is the primary hormone related to pleasure and behavioral motivation and is heavily linked to a Time Before Writing set of programming for mate replacement/opportunistic sex seeking. It’s a completely normal biological function and makes perfect sense in the Time Before Writing scenario.