The beginning of the sentence about time passing very fast:
1. Time flies like an arrow, the sun and the moon fly by. Time flies by so fast, just like a fleeting moment.
2. Time flies, time flies so fast, it seems that in the blink of an eye, we have reached another stage of life.
3. Time flies by in a flash. Time passes so fast that it makes people feel overwhelmed.
4. Time flies, and in the blink of an eye, we have gone through so many years in our lives.
5. Time flies, the years are ruthless, time flies by so fast, it makes people sigh.
6. Time flies like water, and the sun and the moon fly by. Time flies so fast, as if I was still playing in childhood yesterday and have grown up today.
7. Time flies, the years are ruthless, and time passes so fast that people are caught off guard.
8. Time flies, time flies, time flies so fast, and in a blink of an eye we have reached the crossroads of life.
9. Time flies, the years are ruthless, time flies by so fast, we are a little overwhelmed.
These sentences can be used to express the feeling of time passing quickly, and can be used at the beginning of the composition to introduce the theme. Through the use of rhetorical techniques and vivid descriptions, readers can feel the passage of time and the ruthlessness of the years. At the same time, it can also guide readers to think about the meaning of time to us and how we should cherish time.