mental fatigue vs. melacholy.

is it possible to distinguish between mental fatigue and melancholy? is it possible that one is currently feeling both, or that one is causing the other?

i've been writing a lot about what i wish. i've written about what i wish i could do for people, what i wish i could say to people, and what i wish i could show people. this encompasses expression as well as wishful thinking. it is time i do what i can. less wishing and more doing. i must express what i can as best i can, rather than expressing small portions of myself due to lack of expressional means or mediums. all the things i feel i should express, i will do so in person, rather than writting about them here, where i know people can read them. expressing things here is really a cowardice i'd prefer not to admit. this cowardice is still present though, and i shall overcome it to let people know, see, or experience what i feel they should.