Should he choose his wife or his ex?

“I recently had dinner with my ex-wife from decades ago. I cried when she stepped out of her car and when we said goodbye I couldn’t let go. I’m married with one kid still at home. My wife and I love each other, but neither of us are ‘in love’ anymore. She knows that I still talk to my ex and that we had dinner. I’ve thought about her every day since she left years ago. What should I do?”