Your teacher wants you to avoid friendship or love, most likely because new poets have a tendency to get very sappy when it comes to emotion. There are several things that you can write about.
Do you like sports? Does it make you feel accomplished?
Do you like music? How does it make you feel?
Do you make good grades? Do you do it for someone other than yourself?
Do you like the beach? Have you ever been thrashed and lost in the waves?
Have you ever gotten lost in a huge store and felt abandoned?
Have you ever been picked last and felt bad about yourself?
Talk about your fears, that makes some of the best poetry Ive ever read, but pick one and elaborate, tell a story, why are you afraid of it?
The absolute key, is being honest with yourself.
