One thing I've learned with my walk with God is that it's not always easy to mature in faith and become more like Him. Some lessons I had to learn the hard way, such as patience, humility and self-control.
And I think this is also the reason why it's necessary for the physical world to go through the tribulation period before the kingdom of God comes. Like our spiritual life which undergoes sanctification from the moment we receive Jesus, the physical world will also experience the same. Revelation talks about great earthquakes, mountains and continents being displaced and restructured, and huge meteors falling from the sky. I think this pretty much resembles the Christian life in that the earth will go through extreme and dramatic upheaval before the Kingdom of God is birthed.