“Someone has a great fire in his soul and nobody ever comes to warm themselves at it, and passers-by see nothing but a little smoke at the top of the chimney and then go on their way.” — Vincent van Gogh
What makes your mind stronger, and more able to control your emotions, is internal discipline and toughness. No one can teach you this skill; you cannot learn it by reading about it. Like any discipline, it can come only through practice, experience, even a little suffering.