Melancholy

A state of pensive sadness that can be habitual or lasts for a long time. Melancholy shares resemblance with love, nostalgia, longing, and yearning.

Reference:
Coyne, P., Weerts, F., Hassen, S., Wells, J., Griffin, D., Garib, S., ... & Hassen, S. (2009). Where Is the Team?. Journal of Hospice & Palliative Nursing, 11(2), 75.