There are different kinds of goodbye. Meeting someone for the first time, then leaving, there's no attachment. You may or may not see each other again. You could only trust fate.

Parting but with the assurance of meeting again is another thing. There is sadness and longing, whereas there is hope and excitement.

The most difficult is leaving with the reality that the goodbye is eternal. You could only hope that you would meet on the next world, if there is any.