English to Czech Art/Literary Idioms / Maxims / Sayings

This is a famous quote by Oliver Wendell Holmes. There is a complete context below, but usually one see only the ending: "Every achievement is a bird on the wing".

Can anyone explain, what is the meaning of this quote? There is no need to translate it, but I would really need to know the meaning.

Thank you all in advance for your kind help.
With all humility, I think, "Whatsoever thy hand findeth to
do, do it with thy might." Infinitely more important than
the vain attempt to love one's neighbor as one's self. If
you want to hit a bird on the wing, you must have all your
will in focus, you must not be thinking about yourself, and
equally, you must not be thinking about your neighbor: you
must be living in your eye on that bird. Every achievement
is a bird on the wing.