I need help writing a short essay about the topic of whether religion changes lives.
Your main task in this essay is to narrow your topic. There are over 7 billion people currently alive in the world, and there is no way you could know how religion has affected all of their lives, much less the lives of all the people who have lived since the invention of writing some 5,000 years ago. Instead, you need to look at some particular aspect of some people's lives.
If you have been studying the history of religion, you could look at examples of conversion experiences. For example, St. Augustine and St. Francis both had intense conversion experiences which caused them to abandon their earlier life styles and devote themselves to religion and charitable causes. You might argue that conversion experiences are generally positive, causing people to change their lives for the better. Another type of example you could cite would be Alcoholics Anonymous and how belief in a "higher power" has helped addicts on the path to recovery.
Alternatively, you could look at the negative side of religion, and talk about how religious wars and intolerance have caused massive amounts of human suffering. You could give as examples the religious wars in Europe in the seventeenth century or the current situation in the middle east.