Comparison. Whenever we play that game, we lose. Why? At the root, it just means we aren't trusting God, and Saul stands as a reminder of that. Taking a look at him and David in 1 Samuel, we see how badly comparison can hurt us, and also how to avoid it. If we keep our focus on God instead of ourselves, we can enjoy what the Lord has given us now, and not play the comparison game.
Scripture References: 1 Samuel 18:6-9 , 1 Samuel 18:12-16