I Corinthians 4:2 tells us that it is required of stewards to be found faithful. Notice it doesn't say that it would be a good idea for stewards to be faithful, or stewards should be faithful if at all possible, or even, I suggest that stewards be faithful. The Bible says that stewards are required to be faithful!
A steward is someone who is in charge of something that belongs to someone else. Therefore, we are all stewards of everything we have! God created our bodies, our souls and our spirits. He gave us the talents and abilities we have. He gave us our intelligence and personalities and even our looks. God owns everything we are and everything we have. He gives us the ability to gain wealth and therefore even our money is His! The whole Earth is God's by reason of His creating it. When man creates something entirely out of nothing, then we will have something that we own! But, don't hold your breath waiting for that!
God owns; men possess! God owns everything, but He allows us to possess it and He expects, even commands, us to be faithful over all He has given. The Bible warns us explicitly that we will be judged according to what we did with what we were given! If we will strive to see everything as belonging to God, we'll find it easier to be faithful with it.