Think about yourself as follows: "You are an old man."
While I do not deny that a young man can become wise and good, and that Reason is an adequate remedy for the Passions at any age, the old man very obviously has many natural advantages over the youth. He has a certain wisdom that only experience can bring; he is not afflicted by that crusading and (arrogantly) idealistic enthusiasm of the young man; he has learned patience and is slower to anger.
As for his body, it is weaker and grows tired more easily. In one of his moral epistles, the Roman Stoic Seneca considers this also to be an advantage that the old have over the young. He noted that in his own old age he required only a short period of physical exercise each day as his body tired quickly, which, happily, allowed him "to return quickly from the body to the mind." The body only grows weaker with age, but the mind, as Seneca himself in that same epistle asserts, grows better with the passing of time. What folly that we would spend more time worrying about and training that which must necessarily weaken with time, while neglecting that which can strengthen continuously if we would only show it some care and attention!
But perhaps the greatest advantage that the old man has over the young man is one which Nature Herself has bestowed upon him. She has spared him the greater part the carnal afflictions that he experienced in his youth. But again, what folly that some men would reject this merciful benefit and willingly take drugs meant to give them back the terrible libido of their younger days!
The good man lives according to Nature; he does not rage against her. He operates according to the reality of the Universe, not contrary to it. And he accepts that reality, not longing for another one (and one that cannot be). He will say to himself simply 'You are an old man', without adding the clause 'but you would be better off as a young man'.
Old man, rejoice in your old age! You have tremendous advantages over the young man! Your path to Virtue is shorter and easier than his!