Quantum Love (2014)

Pierre has been married for 15 years and has two kids. He still loves his wife and is fulfilled in his role as a father. Overall, he’s a contented man. Until one evening, he meets Elsa. They chat, laugh, and joke around in a way that doesn’t happen every day. Two weeks later, they run into each other again by chance. The same easy mutual attraction they felt for one another is just as strong, and they tell each other as much. A line has been crossed. But Elsa has a golden rule never to get involved with married men, and Pierre wants to remain faithful. They go their separate ways without swapping phone numbers, preferring to let life take its own course. As the line blurs between how they imagine their relationship and what has actually happened, their fantasies start to mingle with reality

Source: TMDb