Do not be slaves to your mind; instead make your mind your slave. Order your mind to be happy and it will become happy for sure.
How to do it?
Whatever is the situation, it depends on you what you choose- happiness or misery. If the situation is not favorable and you allow it to influence your mind, you are choosing misery. However, if you do not allow the situations to influence your thinking process and you change your habitual reaction to such a situation, you will see the reversed effect in the mind and in life.