We'll be honest. While it's often frowned upon in studying poetry, it's very tempting to lump the speaker and Herbert together into one figure. And it seems like a pretty safe move. Whoever's talking rocks a theologically sophisticated voice, musing on the hardships of life and proceeding logically from bad to worse to worst and then up from worst to better to good. And Herbert, being a parson, would be all too knowing about these matters.
Although there's a lot of bleak stuff here, the speaker never loses his hopeful tone. He has full faith in the promise of Easter and doesn't question the power of God to reverse his misfortunes (another quality a parson would be sure to have). In fact, he talks directly to God throughout the whole poem, as if, yeah, it's no biggie to rise up with Christ and participate in Easter, too. Both humble and surprisingly confident, this speaker thinks hard about the past but sees a future full of hope.