The reason for this is illustrated in the following quote:
"Your beliefs become your thoughts,
Your thoughts becomes your words,
Your words become your actions,
Your actions become your habits,
Your habits become your values,
Your values become your destiny."
Bonus points if you can name who said that. Actual bonus points if you can do it without googling it. ;)
But you see how that works? When we believe something, like being "unselfish", that affects our thoughts. We begin to think what we should NOT do in order to avoid being selfish. Which affects our words. We try NOT to say things that will hurt others. Which affects our actions. We AVOID people and places that might cause us to act selfishly. Which create habits. We repeatedly do NOT go near people or things that might make us selfish. Which change our values. We think highly of people and places that help us to be less selfish, and we think badly of people who cause us to be more selfish. Which becomes our destiny: we only do what will help us be less selfish. Which, as you can see, is very selfish! What a conundrum!
Contrast that with love. I won't take you through every step. But you can easily see that when we put things back the way Jesus gave them to us (Love God with all your might, and love other people), we develop beliefs that lead to yada yada... that lead to a destiny of loving God, others, and even ourselves. What a wonderful place to be.
God, help us to form the beliefs that will take us to Your destiny.