This quote explains the negative and positive aspects of the human. We start out in an extremely positive state, but the negative attitude is implanted as we grow and embark on your lives, socially and intellectually. These are learned behaviours that are instilled as beliefs.
We can choose to maintain the negativity produced by our minds or, hopefully, as we grow, we learn that the kind, loving, side of our personality has more benefits for everyone. Sometimes, it is a battle between the two conflicting beliefs.
There may be occasions in your life where you are struggling with contradictory beliefs, or you have garnered new information that conflicts with existing beliefs. This causes mental stress and discomfort, as you try to make the decision on which wolf to feed. In psychology, this is called cognitive dissonance. (Wikepedia)
As the quote states, "it is the one you feed that wins." Therefore, if you find yourself feeding the wolf of anger, jealousy, greed, resentment inferiority, lies and ego, this is the time to take a look at what is motivating these feelings. You have downloaded this behaviour as a survival technique at some point in your life. Is this working for you? What are the benefits in this line of thinking? You will not achieve any peace within, if this is the way you choose to continue to live. You are cultivating loneliness, depression and illness, living in this manner. Look for way to get out of your head.... go for a walk in nature, be around people and observe, pay attention to what is going on outside of yourself and your thoughts.
If you persevere, if you take the time to look into your inner workings, and eliminate negativity from your life, you will be feeding the good wolf.... Joy, peace, love hope, humility, kindness, empathy and truth.
It is all up to you. You choose how you want to act and be. You have the power to choose which wolf you will feed.