The correct answer is to this open question is the following.
Taking into consideration what I have learned about happiness, suffering, death, and the meaning of life, the piece of advice that I can give to the following people in various situations is the following.
1. Your sister is an overachiever. Being on top of the class is what makes her feel fulfilled. However, she got lower grades than usual for this quarter. She is extremely saddened and discouraged by this and becomes withdrawn and aloof.
Recommendation:
I would tell her that there is more to life than academics. It is ok to have excellent grades, but the important thing is to know what to do with that knowledge. How you practice it and put it to the service of other people. That is what really counts.
So she should start applying all her knowledge in real-life situations. She should open a small business, she could create a small community project, and when she realizes the benefit she is producing to the benefit of many people, she will feel that her life has sense again.
2. Your best friend is dating a married man. Despite her family's disapproval, she does not want to break up with him. She says that he is the only one who makes her very happy.
Recommendation:
This is a tough one because when the heart is involved, it is very difficult to convince using reason or arguments.
But what I would tell her is that she has to be very conscious that he is not going to ask his wife for a divorce. That he is only using her just to have fun and nothing serious is going to result from that relationship. And of course, that one day -sooner or later- it is going to end. My recommendation is that she has to be prepared for that moment.