1. You must believe that 30 years old will come very soon, whether you are playing Warcraft, cs or dancing in the bar, even if you try to look younger, time will always leave a mark on your heart, pretending can never change the fact. There is only one way: get prepared in advance, even if you are only 18 years old and still look very young. After 30, you will be just like an old pearl waiting to be discarded. So if you don't prepare mentally in advance, you will end up being annoying to everyone.
2. Do not refrain from doing small good deeds, nor indulge in small evil acts. No matter how deep your understanding of life is, in many aspects, it's best to listen to your parents' advice, or even follow their instructions completely. Apart from the traditions left by our ancestors, they have lived several decades longer than us, and their understanding of this cruel society far exceeds ours, even if they are not highly educated. After 30, you will find that your views on everything are basically the same as theirs back then. By then, regretting will be of no use.
3. You must know how many friends can help you, how many friends are just eating and drinking with you, how many friends are dispensable, and how many friends need to be careful about. It's better to figure out what their families do, because no matter what kind of friends they are, there will be a day when you need them. After 30, you will find that those successful people always have a large network of relationships around them, and almost all of them are maintained by friends.