This one is actually a good question. Well first, this is from the great gatsby. Fitzgerald was trying to give a balance view in the beginning of who the great gatsby was. And even the author, he lived a wonderful life that is why he related that into Caraway's character, having the same background as him.
The poet compared imagination to a soaring bird because imagination is limitless, it can do anything and go anywhere, much like a soaring bird, who has the freedom and capabilites to do anything. Both are completely free of bounds.
Things that should be avoided are phrases like:
in my opinion
i think
i believe
and definitives like: completely, never
