(remember that you can interpret this any way you want. However, there is the meaning I meant to interpret, in which if you are confused, is this:
The poem basically talks about how human life is only slightly different than being a goldfish, for in your life you will be going in circles, and most of the time you are stuck in the glass bowl with no means of escape. However when you are a goldfish, you have 3 months of memory (seven seconds is an exaggeration from legends and myths) and you'll easily forget the pain you've faced in the past, only to experience the loneliness and isolation of being stuck once again. And if you ever wanted to die, it'd be so easy since you're so fragile.)