This poem is roughly in common meter (check out "Form and Meter" for more on the technical aspects of common meter). "Amazing Grace" is also in common meter. Sing the first stanza to the tune of "Amazing Grace" and you’ll see for yourself. Common meter is very popular in hymns since it is easy to sing along to and has a nice, sing-songy rhythm.
However, as you probably noticed, the fact that most of the poems by Dickinson have a similar sound to hymns is pretty strange considering their intensity and negative mood. Dickinson was fully aware that she was borrowing from the hymnal tradition in writing like this. It would be as if your favorite band wrote a song to the tune of the national anthem – everyone would notice and there would be a point. In Dickinson’s case, this rhythm gives the poem a smooth sound. It’s almost chant-like in its rhythm, fit for a congregation; however, its content is decidedly not. It sounds like a hymn, but only until you make sense of the words.