Your imagination can be as big as you make it I know, I used to tolerate it in the far corner in the back of my head my insecurity wrapping around me. This stanza means, that this person is scared, and insecure about themselves. Stuck in their imagination, with anxiety.
But I sighted a far off horizon where the sky-line finally meets the sea and my heart throbbed with a powerful burning desire to travel this immensity. In this stanza, the person is still afraid but, she knows what a magnificent world we have. And she wants to explore but, something is holding her back.
I trashed with the barrier around me and cradled my wings along the gentle wind then soared to the maximum reaches with rapture, with power, with ease! To sum it all up, the person has gathered all its confidence and decided to reach his/her’s full potential. The person knows not everything is going to come to her on a silver platter, so she decides to strive towards her goal to discover her world.