I don’t know why I’m studing at school. My goal is not clear at all. I have no idea how I can be beneficial for my society. In fact, I wanna know how I can motivate myself to study harder and be happy in my life. (I’m studying in engineering with application in biology)

First, I would like to congratulate you for asking, essentially, “What is the meaning of life?” Far too many people live their entire lives without ever questioning the choices they choose and the decisions they make.

In my view, there are three basic sources of meaning: Personal, Social and Universal. We’ll tackle social first, since it’s the most straightforward.

I – SOCIAL:

The way to live a meaningful life in a social context is to help other people, and there are six or seven major avenues I would recommend to pursue this:

  • The Environment – this may be the most important question for all of us right now. How can we save the environment before it is too late? I would note that engineering might be a good pathway towards this issue –in terms of creating cleaner technologies, or new ways to deal with pollution.
  • Peace – We need to stop killing each other. People have been working on this for thousands of years, but that doesn’t mean that it’s insoluble or that we should give up.
  • Health Care – Many people around the world are dying from preventable diseases. If you’re interested in medicine, your background in biology could feed into this.
  • Poverty and Social Justice – We live in a world where some people are incredibly wealthy and others live in abject misery. No matter where in the world you live, there are simple direct things you can do to help make life better for the poor of your community.
  • Music or the Arts – The world can always use somebody who brings a little more beauty into the world.
  • Education and Mentoring – Even if you’re not enthusiastic about your own education, you might feel better about passing some of it on to a younger generation. When we teach or mentor those younger than ourselves, we shape the future.

II – Personal

For some people, the standard modern human narrative of get educated, get a job, support and raise a family is enough, for others it is not. Particularly in college, many people discover they have lived their entire lives by the decisions of someone else. In my view, we all have limited lifespans and none of us knows he or she will be alive tomorrow, so I think we all have a right to pursue our own destinies –given that we are not harming or exploiting others. No one has the right to force you to live the life they want you to live.

That said, simply abandoning the things you are involved in now is not going to make you any happier. You need to figure out what you want first, and pursue it second. I recommend the following: First, buy two small blank journals. For the next several months, make a point of trying to remember all your dreams, and to write them down in one of the books as soon as you wake up. Feel free to add pictures or whatever else will help make the dreams more vivid to you. In the other book, write your best and boldest daydreams about life –and also your biggest and most secret fears. Set aside some time every day to meditate on these two books and they will eventually tell you who you are and what you want.

III – Universal

This is the big hard question –what is the meaning of life in the most universal sense. Why are we here? For me as a Christian, I take my answers largely from my faith. If you come from a religious tradition, you might study the holy books of your own faith for some answers. If not, you might try reading some of the great works of religion and philosophy of the world. Personally, I recommend Plato, the Tao Te Ching, Ecclesiastes and the New Testament from the Bible, Kierkegaard and the writings of the Sufi mystics as good places to start.
Good luck to you. You may find that you are a philosopher –one driven by nature to search for meaning.

Why do philosophers such as Nietzsche doubt everything?

I’m not sure that’s the right way to characterize Nietzsche, but skepticism –doubting things –is one of the four essential services philosophers provide to a society (the other three are mystical guidance, system-building, and practical guidance).

In general a society cannot function smoothly if all things are questioned at all times. If things –social structures, moral values, traditions, customs, and so forth– are taken for granted, however, then they can become corrupt, stagnant or obsolete. By casting a skeptical eye on things that everyone else takes for granted, a philosopher such as the one you mention clears out a society’s accumulated conceptual detritus and paves the way for progress.

Other famous skeptical philosophers include Socrates, the Zen Buddhists, Chang Tzu, Sextus Empiricus and David Hume.