The speaker looks back with longing at a childhood of cartoons, outdoor play and imagination, when a paper plane could lead the way. The present is much tighter and angrier. They stand digging their nails into their hands, ignoring a mother's instructions, pushing against a world that seems to be falling apart, and doubting whether their own writing counts as art at all.
Most of the poem, though, looks ahead. The speaker's biggest fear isn't failure but ordinariness: spending years at a job they hate, counting wasted hours, never feeling anything strongly. They hope to avoid that fate, and to reach old age with a soul that hasn't gone cold. The closing image of ambitions "as low as my room's ceiling" is neat and a little claustrophobic.
The mood is restless and wistful, with a stubborn thread of hope. The title, "not so high hopes," feels ironic, since the speaker's hopes are actually quite large.