St. Thomas says

" It belongs to perseverance to persevere to the end of the virtuous work, for instance that a soldier persevere to the end of the fight, and the magnificent man until his work be accomplished. There are, however, some virtues whose acts must endure throughout the whole of life, such as faith, hope and charity, since they regard the last end of the entire life of man."

Only the person who perseveres can achieve great things. The greatest thing is eternal life. To achieve eternal life requires the greatest amount of perseverance.