Once upon a midnight dreary, while I pondered weak and weary,
Synonym: tired. Used not only about the body, but also about the mind. If you are weary from practicing football, you don't feel like practicing football for a long time. Your mind is tired, not just your body.
Respite - respite and nepenthe from thy memories of Lenore!
Synonym: break. In the poem, used in the sense of "stop doing it, please". "respite and nephente" basically means "stop doing that and forget about it".