For a lot of different cultures, the eagle is used to symbolize a pure spirit. It is a majestic animal, and can see clearer than any other bird or animal - it has eyes that are eight times sharper than human eyes. It is this clarity that is used to signify such a pure spirit.
It can be difficult to keep sight of what is important in life, but the eagle can serve as a reminder to see what is important in life and to remain true in spirit.
The past, present at future is all things that can benefit us if only we choose to examine them with a clear vision, in order to learn from them.