You aren't born with a set path to go, rather it is carved by every nuance in your mind. If you wish do delve deeper into the reason of why you aren't constricted to a singular path, you may examine multiverse theories (which I don't believe is easy). You are given unlimited choices in life, and you have many things which you must choose. One thing you may choose over another simply because it better suits you, and some things you may choose because they will benefit you more than others.
Personally I would not attempt to cause major change in the world, as you cause change in everything simply by thinking or doing. Refer to the Butterfly Effect. A butterfly in New York flaps its wings, and that small change is enough to cause a hurricane to sprout in the Atlantic Ocean.
You have a reason to live, whether you do good or bad, it is still change. A man wonders his whole life what the meaning of his life is. He reads books, helps people, and causes change, all in the process of searching for his reason. The reason we exist is to search for a reason to exist. It's one of my favorite paradoxes. Of course, the other reason we live is to procreate, and this does not benefit us in the slightest, but we do so to benefit the earth. Future generations also search for meaning in this lonely universe when that search for meaning may be the true meaning of life.
No human has a preset path, we are like robots. A robot attempts to climb stairs, and overcalculates the height. He falls over. The next time, he undercalculates it. He falls again. By figuring out by how much he fell each time, and why he fell, the robot can sucessfully climb the stairs, assuming further stairs don't have varied height. If he reaches such a stair and falls again, the process continues. The same thing exists with humans. We aren't born with innate capabilities to carry out our lives prefectly. Then we would not be humans, our faults and lack of knowledge is what makes us human. We wonder things in philosophy, and there are hundreds of theories in each subject. Never finding out which one is correct makes us human, because there is no correct answer to these things. We are born with mechanisms such as limbs, and are also born with senses. Without them, we wouldn't follow any path. They make us human.