You are in control of your thoughts. You choose how you feel and you choose how you react to things. If you have one bad thought, even for just a second, more bad thoughts are welcome to appear. One bad thought will turn into a chain of bad thoughts if you let it. If you feed on these thoughts, you will become so used to it that you will always find yourself feeling this way. Stop these thoughts, no matter how impossible it seems.
(Source: itswhatyouleavebehindwhenyougo)