Why do we need to study the past?

As the old adage goes "those who forgot the past are doomed to repeat it." Studying history not only helps us to recall the events that have passed before us, but it gives us great insight into humanity at large. There are many reasons to study the past, and I'll outline a few here.
First, the past has shaped our present. An understanding of, say, the political tensions of the Cold War is actually very pertinent today, with countries like North Korea and China beginning to create nuclear weapons and Russia being accused of spying and political interference.
Second, history does tend to repeat itself, in a broad sense. By seeing the trends and events that have happened in the past, we can predict what sort of things may happen in the future.
Finally, history gives an understanding of human nature. Historical events and the responses people have had to them give an incredible insight into the human condition and informs psychology, sociology, and much more.

There are several reasons why it is important to study the past. One reason is that many events repeat themselves in some ways. For example, many of the causes of World War II were similar to the causes of World War I. If we would have learned from the actions that led to World War I, we might have been able to prevent the outbreak of World War II. Another example deals with the start of economic problems. Many recessions and/or depressions have similar causes. For example, some of the causes of the Great Recession of 2008-2010 were similar to the causes of the Great Depression in the 1930s. Preventing future mistakes is one main reason to study the past.
Another reason for studying the past is that people should be able to see how past events have relevance in their life now. The past should serve as a personal guide to the future. If a person learns from the mistakes of others, they can hopefully prevent making those same mistakes in their life. If a person learns from the actions of others, he or she can develop a personal blueprint of how to live. For example, a person can learn from poor financial decisions others have made in order to avoid making those same mistakes in his or her life. Studying the past can have a direct impact on your life today.