I suspect millions today could echo your classmates' comments, because life for them hasn't turned out the way they hoped it would. Sometimes it's because of a broken relationship, an economic reversal, an illness, or some other obvious cause.
But often they can't put their finger on the reason for their discontent. The problem is that they pursued goals in life that have failed them -- goals that promised to bring them happiness and peace, but never did. Their goals were inadequate -- or even deceptive and false. They reached their goals, only to find that it left them empty and bored.
Take, for example, a person who and makes money and financial success his or her goal in life. What happens if the person reaches that goal? Does it bring satisfaction and peace? Perhaps it does -- for a time. But in the end, the person is like the writer of Ecclesiastes in the Old Testament. He had all the wealth and power anyone could ever want, but it left him empty: "Utterly meaningless! Everything is meaningless" (Ecclesiastes 1:2). Only when he turned to God and sought His will for his life did he discover lasting joy and peace.
And the same is true for us. If you have never done so, turn to Jesus Christ and commit your life to Him. Then ask God to help you point others to the new life and peace He alone can give to those who put their faith and trust in Him.