The famous Jewish sage Ben Zoma said: "Who is a strong person? Someone who subdues his impulses to do wrong, as we find expressed in the verse: 'Someone who doesn't lose his temper is better than a strong man, and someone who controls his spirit is better than someone who conquers a city.' "
He is describing a trait that applies only to people: Courage. Animals exhibit physical strength. But courage, spiritual strength, only applies to people.
Physical talent can be developed, but the potential is basically inborn. Either you have the potential to play professional basketball or you don't. The basic talent must be there.
But when it comes to spiritual strength, everyone has the same opportunity to excel. Wherever you stand spiritually, there is a challenge. Though some people, due to place of birth, education, etc., would seem to have it easier, in actuality each person has his own tests which are perfect for him.
An amazing story is recorded about Rabbi Chaim Vital (16th century) and the Arizal (Rabbi Yitzchak Luria). The Arizal was the great teacher of Kabbala in modern times. Rabbi Chaim Vital was his primary student, who recorded almost all of the Arizal's teachings. Once Rabbi Vital asked the Arizal the following question: "If the Talmudic Sages with all their greatness and levels of holiness weren't able to bring the mashiach (messianic era), then how are we going to be able to?"
The Arizal's answer is even more understandable today that it was then. He answered: "In the time before the mashiach it will be so challenging to correctly observe the Torah that the observance in those times will have more power than it did in the earlier times. Even though it may not be done as completely, but because it will be so difficult it will have the power to bring the mashiach."