我的理解和译文：

原诗：

Had I not seen the Sun
I could have borne the shade
But Light a newer Wilderness
My Wilderness has made 

试着把语法补齐：

Had I not seen the Sun
I could have borne the shade
But (the sun sheds) Light (on) a newer Wilderness
(that) My Wilderness has made

译文如下：

（阴影与原野）

若不是看见太阳
我本已习惯了阴影
可是阳光却照亮了一个原来不知道的原野
我的早已在那里的原野

 

个人理解，望斧正。