People will let you down.
An important lesson that we have all probably experienced in life is that people will let you down. Whether it be in our personal lives, or lives outside of our families and homes, we have to make sure that we hope for the best from everyone but plan for the worse to happen. It might sound like a cynical way to live, but in this world, and especially in this day and age, we have to insure our own interests, which means not depending on anyone else to get the job done but yourself and God. When we learn not to depend on others we learn that we have the freedom to do what we feel we need to get done, and being the only person responsible for whether you fail or succeed can be a great thing! Of course there will be situations in life where we will need others, but always keep in the back of your mind that no one is perfect, and anybody that is human is capable of making mistakes and letting you down.