In the second stanza, the speaker is born into sin; therefore, his "tender age in sorrow did begin." Before this (in the first stanza), the speaker deals in the generality of "man"; however, the second stanza makes the fall personal. With this birth into original sin came "sorrow," "sickness," and "shame" when the speaker became "most thin." Of course, this issue can all be resolved if he can "combine / and feel this day thy victory." Grafting his own "wing" to Jesus, the speaker can truly obtain happiness in heaven because the speaker will have participated in Christ's victory over death.
With thee / Let me combine / And feel this day thy victory: / For, if I imp my wing on thine, / Affliction shall advance the flight in me.
However, indicated by the words "Let me" and "if" and "shall advance," the reader can be assured that this has not happened quite yet. Still, the speaker's hopes have been well documented here.