The hearth and the Salamander can also mean happiness and if Montag chose to be happy or not. The two things in his life his home and his work. Did it really make him happy. He chose happiness over this home and his work by reading the books.
TRAIN your mind to see the good in every situation. It won't come naturally, you WILL have to work at it, but eventually it will become second nature and you will have joy in your life even when things aren't going your way.