Friedrich Nietzsche said this quote
“ Examine the lives of the best and more fruitful men and peoples, and ask yourselves whether a tree, if it is to grow proudly into the sky, can do without bad weather and storms: whether unkindness and opposition from without, whether some sort of hatred, envy, obstinacy, mistrust, severity, greed and violence do not belong to the favouring circumstances without which a great increase even in virtue is hardly possible. The poison which destroys the weaker nature strengthens the stronger – and he does not call it poison, either. ”