What does the speaker mean by "No later light has lightened up my heaven" in this excerpt from "Remembrance" by Emily Bronte?

No later light has lightened up my heaven,

No second morn has ever shone for me;

These lines suggest that there hasn't been a second lover for our protagonist, ever since her youth. She remained faithful to him, hasn't moved on and found herself another man. She isn't happy now, though, however, she won't break her promise.