It wasn't necessarily a bad poem. You definitely need to work on your imagery, though. Steer clear of all that darkness and death stuff, because you seem to have picked up quite a few bad habits there.
Write a poem with completely different themes, or use a metaphor. Don't copy one from anyone else.
If you're stuck for ideas, try a spider diagram. Write your central theme, and then write all of the words you associate with it until you come to something completely different that you could write about, or use it as a metaphor.
Also, writing always gets better as you grow more mature. The more you write, the better you'll get. Good luck.
