I think the sad sentences are as follows:

1. My sky is a bit gray today, and my heart is in the season of falling leaves. I don't know how to spend tonight. All the lights have been turned off.

2. Feelings are like white rice, romance is like food on the table. When people are hungry, they will think about eating, but after eating, more people like to comment on whether the food is delicious and ignore the taste of white rice.

3. I try to forget you, but the memories always make me unable to let go.

4. Our love is like a voyage that cannot reach the other shore.