There is a popular saying: 'Nothing is impossible.'
This is actually contradictory. How can 'nothing' be impossible?
You need something, such as a target, to test whether it can be achieved.
But we can explain the above statement philosophically - it's all about attitude.
There are plenty of examples where someone has achieved what seemed to be the impossible.
This is why people say that 'nothing is impossible'.
For example, who would have thought about an aeroplane before the Wright brothers invented one?
Then there was Thomas Edison, who invented the light bulb, and physicist Albert Einstein, whose Theory of Relativity still forms the foundation of many scientific discoveries.
All these show what you can succeed if you concentrate on a task.
You may think that it's not possible to get high marks in an examination or be a more optimistic person.
You may consider yourself a failure, but you can change things - if you work hard, nothing is impossible.
Although how much effort you have to put in depends on your abilities, you can lead a much happier life if you do your best and strive to achieve your goals.
Of course, there are impossible dreams. Do you think you can stand on the moon with a blink of your eyes?
But there are still many things that are possible - although you may not think so.
Whether the impossible is truly impossible or not depends on you.
Adrian, 16, from St Mark's School, is a member of the Hong Kong Outstanding Students' Association