Eternal Sunshine of the Spotless Mind (2004)

Joel Barish (Jim Carrey)'s ex-girlfriend Clementine (Kate Winslet) erases all memories of their two-year relationship with a mysterious medical intervention. After learning this, Joel is very sad and decides to have the same procedure applied on himself. His days with Clementine pass before his eyes when he goes to sleep to erase all his memories. Joel realizes he doesn't want to forget Clementine and tries to stop the intervention.