Saudade
Finally found a word to embody the complexity of emotions I feel when I have to separate from a person / place / project.
Saudade is a deep emotional state of nostalgic or profound longing for something or someone that one cares for and/or loves. Moreover, it often carries a repressed knowledge that the object of longing might never be had again. It is the recollection of feelings, experiences, places, or events that once brought excitement, pleasure, and well-being, which now trigger the senses and make one experience the pain of separation from those joyous sensations. Saudade describes a feeling both happy and sad.