Mark 9:35 (NKJV)
35 And He sat down, called the twelve, and said to them, �If anyone desires to be first, he shall be last of all and servant of all.�

Christ explains to His disciples those who are considered the greatest are the people who put aside themselves to serve God and place the needs of others first.

It is the desire for God which is the most fundamental appetite of all, and it is an appetite we can never eliminate. We may seek to disown it, but it will not go away. If we deny that it is there, we shall in fact only divert it to some other object or range of objects. And that will mean that we invest some creature or creatures with the full burden of our need for God, a burden which no creature can carry. �Friar and author Simon Tugwell, The Beatitudes

The above words point to the fact that when we place ourselves first, we tend to invest in things other than God to meet our needs. In making ourselves first, we make ourselves last with God. When we surrender to God and perform His will then we make ourselves last and become first priority with God.