Happiness is real only when shared

As you may have figured out already, It takes me a while to understand certain things. Like for example, Altruism. That you can only be truly happy when you aren't hurting someone else in the process. Chris McCandless, better known as Alexander Supertramp ( a book and movie of his journey titled "into the wild" for more information ) said Happiness is real only when shared. Now I didn't understand that completely when I saw the movie. I mean I understood the meaning, but I had no idea how to cultivate Altruism in me. The buddha says Altruism begins with realizing that your happiness depends on the happiness of others. I truly feel the buddha is the greatest teacher I've ever had. The mark of a good teacher is the ability to decompose the concept into simpler concepts. That his teachings are helping people even 2500 yrs after his death says something about the Buddha that I cannot express in words.

My room mate has been unable to walk for a few days now. Almost every day, and every night, his friends come over and cook for him, chat with him, and eat dinner with him. Its probably what everyone's friends do, but it begs the question, what is it that stops us from being this nice to everyone, and not just our friends? Why do we dislike people? Now I'm not saying I love everyone under the sun. Far from it. However, I am starting to be mindful of my negative feelings. I wonder why I dislike someone. I wonder why anyone dislikes someone.