Why should I return to my marriage if I'm no longer in love with my spouse?
The loss of "in love" feelings is common to those who have been through an affair. It's also common that many doubt whether they were ever genuinely in love with their spouse, especially following an affair that involved a strong emotional connection. Most likely, passion had diminished in your marriage before your affair started and now the emotional jolt you got from the affair makes your marriage feel void of love.
But it wasn't always that way. Your relationship with your spouse started out with a passion you've forgotten. The question is: is it possible to get it back, especially after everything you've been through?
The answer is probably yes if you're willing to put effort into restoring the relationship you had with your spouse. In fact, it's possible to experience greater intimacy with him/her than you've known before. It won't be easy, but the payoff is wonderful.
But why should you have to work at loving your spouse when it seemed to come so naturally with your lover? Because the passion you experienced in the affair was supercharged in a way that cannot be sustained over time. No relationship can sustain that level of emotional euphoria, despite what popular songs and movies sometimes tell us.
Not every marriage can survive an affair. Not every marriage should. But it's too soon to give up if you've simply fallen out of love. If that's your main reason for leaving your spouse, I'd encourage you to first give time and effort to see if love can be rediscovered in your marriage.