One possible version：

Here are the meanings of Chinese characters in the drawing: The first sentence says the sky is most beautiful just before sunset. The second means the citrus fruits are most sweet and fragrant at the end of a year. That a man should be even more vigorous in trouble or at older age is what the last two sentences want to express.

What we can learn from this drawing is that all of us should stay vigorous no matter what difficulties we are faced with or how old we are. We are as young as we think we are so long as we take up new studies and new interests, for exercising our bodies—through manual labor and other physical activity--will stimulate our brain and keep us in good spirits.

So forget about our age. We should be proud of the years of experience we've gained.