I am sad.
I am melancholic.
What is the difference? I do not know.
I am not upset, just ...sad. I make myself think of happy things and happy moments but instead of becoming happy I become sad, having a sense of loss and futility, knowing either I won't ever experience those moments again, either they're too far from reach now, in this moment. I do know I can try and most probably succeed to attain (some of) those happy goals, but just the fact that they are not immediate, or better yet instant, saddens me.