Paul's desire is to tell the Philippians that he if fine. He expresses his gratification of the gift they have sent him. He wants them to know that this isn't the source of his contentment. He is content in all circumstances. His contentment comes from the content that exists within him.
Most people, even Christians, never get to this point. I suppose the world keeps telling them that they must maintain a certain lifestyle. There are things the world says that everyone deserves. The world is wrong.
Contentment is never long lasting as long as we think that there are advantages which are inherently ours. I can't be content if I am hungry when I deserve a good meal. I can't be content when I see someone drive by in a car while I am forced to walk. The funny thing is that abundance in things doesn't actually make our contentment any greater. We always have the capacity to want more than we have. We are always looking at the horizon and never satisfied with where we are for long.
Yet, Paul says he is content whether he has an abundance or nothing at all. He says that he is able to do that with "Him who strengthens me." That makes me think that I and other Christians rarely really depend upon the strength that Christ provides. We look at ourcircumstances just like the rest of the world.