Why is there no ideal time of the day when all students should study?

Ithink this is true. 

People can make sacrifices like not going somewhere even when they want to, or not eating a certain food, or skipping something for a friend or family member. you can determine it yourself when you are thinking about what to do, such as: do you really want to go to the (input whatever) lets just say zoo, or do you want to your friend study so she can go to the dance next friday? (input whatever)the value in making sacrifices is being a true friend or family member, and seeing how it will affect others. it is very important!