to know we are responsible for the lives we change. (3-4)
Demeter wants Hades to know that he has to consider the repercussions of his actions before acting. He took Persephone without considering what it would do to her and, by extension, the earth (which she, goddess of agriculture, cursed into famine). Thinking before you act sound like something you learned as a kid, but we guess the gods didn't get a chance to go to grade school.
I see clearly the trail you planted (7)
The "trail" that Hades planted isn't a literal trail. Demeter is talking about the results of his choice to take Persephone down to the underworld. His actions left "seeds" that grow into reactions. Isn't it the same for us? Our actions, too, have repercussions. Everyone has the power to plant a "trail."
Believe in yourself, go ahead—see where it gets you. (14-15)
Why tell a god to "believe in himself"? Doesn't he already know he exists? Yes, but perhaps Demeter is being sarcastic. She knows that he thinks that he is a god, a being that has the power to do whatever he chooses. But, she says, the downside to that power is all the destruction that it can bring. In the end, it might not bring him anything but sorrow.