The mood of this well-known poem by Dickinson is clearly happy and upbeat. Note how Hope is personified as a "thing with feathers-- / That perches in the soul." This image of some kind of bird that sits in our soul and keeps on singing, no matter what is going on outside, creates an uplifting, encouraging mood:
And sweetest--in the Gale--is heard--
And sore must be the storm--
That could abash the little Bird
That kept so many warm.
Dickinson thus uses the mood she creates in this poem to link in with her meaning, which is the way that hope is a force or power within us that can remain unextinguished no matter what troubles we are facing. Note too the way that the final stanza presents hope as something that does this great service for us but never asks for anything in return:
Yet, never, in Extremity,
It asked a crumb--of Me.
Even though hope is always giving, it never asks for anything from us in return. This is clearly an encouraging and happy message which is supported by the mood of this poem.