The song with Meera and Vivaan remembering different scenes of their relationship. Him all the sweet moments and her the painful ones. Without words the writers managed to show why he is hopeful and she despairs of ever making it work.
There have been other beautiful scenes but for me this comes right there on top with my all time favourite - one where Meera's Kabaddi is disapproved by every family member and Naina from Dangal is playing. That scene broke my heart.