From birth, we have a natural affinity to the things of this world, mainly because of "The Fall" of Adam. Santa Claus at Christmastide, just like Peter Cottontail at Eastertide, are both secular icons misrepresenting sacred, holy days in Christian faith and culture. However, until one experiences a new birth in Christ, by believing in their heart unto righteousness and confessing with their mouth unto salvation, they will not experience the freedom in Jesus Christ, the living, Anointed One who is the embodiment of Christmas, Crucifixion and Resurrection: born to set His people free by dying on a cross as the sin offering in our place, yet is risen and lives forever. Jesus' whole point by coming that first Christmas was to restore us to God, just as it was in the "Pre-Fall", before Adam ever sinned. Often, we do not accept Him because we think it is too hard to follow Him, yet He promises that his yoke is easy, and His burden, light, If we but make Him our Lord and Savior. It is really hard to live in faith when we are more comfortable with that which we can see. Thus, we learn to trust the tangible rather than the spiritual, which by the way, is the source of everything tangible. So, in answer to your question, our sin nature, inherited from Adam, yields a predisposition to selfishness, covetousness, pride, etc. Thank God for the second Adam, Jesus Christ, who reconciles us to unbroken, right relationship with God, our Father.