They certainly try to predict human behaviors. As you go into more depth in your psychology classes, you will cover the thousands of different studies that people have conducted in an attempt to predict human behavior and explain why we behave the way we do. You will be asked to memorize and ponder many different theories that come from those studies, and it will be up to you to decide which is the best one, which one you feel best describes that behavior.
For example, take motivation-the why behind all of our actions. There are many, many different theories on motivation. You have Maslow's hierarchy, where he states that basic needs to be me fulfilled before we can feel motivated to achieve higher goals, then there is the instinct theory, that states everything we do is because of an animal-like instinct that drives us to do it. Take the nature/hurture discussion, where people are trying to find the balance between genetics and environment on behavior. All of these will have studies to attempt to prove their take on it all.
It isn't until psychologist understand the why behind our actions that they can step in to try to control those actions. Psychologists probably wouldn't like the word "control"; "better" or "improve" would suit them better. They want to help people be happier, more fulfilled, and healthier. And they try to do that through medication, therapy, and different practices.