1) Most of the people you know growing up through your PhD and postdocs will suffer horrible career deaths.
2) Being a good or bad person has no impact on how likely this is to happen.
3) You will travel to many exotic and interesting places, but most of your time will be spent inside, talking about things that will sound intensely boring when you try to explain them to people who are not already interested.
4) As you progress, you realise how much of the power structure that you know relies on academically incestuous relationships.
5) If you are female, there will be guys who are very keen to help you. It will become apparent why before long. Eventually, if you are lucky, you will get to see one of them make a mistake and kill his career.
6) Every so often, a huge new fire-breathing idea comes into the world. When this happens, you want to be moving forward in alliance with the metaphorical idea-dragon, not cowering in your castle trying to keep a non-viable research area alive.
7) You will love you career, but many people will think you are deeply strange for wanting to spend so much time and energy on something which is painful to watch.