Rewatch, cry, read fic, cry, find people to cry with, cry, RP every possible AU/canon divergence. But more seriously, I find that talking the series out with other fans helps a lot! Brings a new perspective and depth to what you've watched, and makes you appreciate it in a different way
Fantine's Death and Epilogue from Les Miserables are both guaranteed to make me cry. Particularly the 2010 live version. The emotions are so evocative!
"To love another person is to see the face of God." Goosebumps every time 😫