Answer:
I'm not exactly sure what you are reading but to my best understanding, the speaker means that maybe his/her entire high school life was full of sadness or -- how is says here -- melancholy feelings.
Explanation:
Melancholy literally means some sort of sadness that usually appears out of nowhere and hangs heavy on the heart or the soul. The speaker might be saying that he finally graduated from a point in his life that he was particularly down on his luck and now he finally feels a bit better. If you were to look at it from a high school point of few, maybe the speaker graduated from high school and that place served him as a place of distress and it was finally gone. I do hope this helps out a bit.
