The speaker is caught between past happiness and present bitterness. Looking back, he realizes he once lacked things he loved, but he didn’t know he lacked them, so he was genuinely happy. What hurts now is not the lack, but forgetting that earlier happiness and accusing fate for not making him something freer, like a bird or a tree. He pulls himself back from that anger, afraid of offending God, and asks how anyone can regret the past when it made them who they are. Everything he was still lives in him. The old childish joy has not died; it rises again at the sight of a green field or a green tree. The mood is reflective, gently self-correcting, and finally peaceful, with a soft reverence for nature.
All that I was I am — Summary
Hateful it seems now, yet was I not happy? Starved of the things I loved, I did not know I loved them, and was happy lacking them. If bitterness comes now (and that is hell) It is when I forget that I was happy, Accusing Fate, that sits and nods and laughs, Because I was not born a bird or tree. Let accusation sleep, lest God's own finger Point angry from the cloud in which He hides. Who may regret what was, since it has made Himself himself? All that I was I am, And the old childish joy now lives in me At sight of a green field or a green tree.