There are admirable potentialities in every human being. Believe in your strength and your youth. Learn to repeat endlessly to yourself: "It all depends on me."
It is not always by plugging away at a difficulty and sticking to it that one overcomes it; often it is by working on the one next to it. Some things and some people have to be approached obliquely, at an angle.
Know thyself! A maxim as pernicious as it is ugly. Whoever observes himself arrests his own development. A caterpillar who wanted to know itself well would never become a butterfly.