There is immense pressure on a preacher to be "good" at what he does. There is the identity issue. What are you if you are not a good preacher? There is the attendance issue. What happens if people will not stay at your church? There is the money issue. What happens if people don't stay at the church and you have to look for another source of income?
Perhaps the biggest pressure is to relieve all other pressures by copying a favorite, "successful" preacher. Through podcasting, the way things typically go these days is a handful of preachers become the most popular in a given Christian sub-culture. They are deemed "successful" pastors and preachers. These preachers are the ones the majority of like-minded preachers listen to.
So, if you want to be a "good" preacher, feel secure in yourself, maintain attendance, and keep your income, just imitate the best preacher out there in the podcast world! Just do what Jack Graham, Matt Chandler, John Piper, Chuck Swindoll, or [your favorite preacher's name goes here] does. Use their tone, their body language, and their way of structuring a sermon and you're all set.
It is easy to imitate the powerful aspects of your favorite preacher's preaching. It is hard to be yourself. But being yourself is exactly what you need to give yourself freedom to do. Jesus died for you and if you've been called to preach, Jesus called you. Jesus created you to talk a certain way, use a certain tone, use certain body language, and even think in certain patterns that may be different from others.
Most of your week is spent pastoring church-members by conversing over coffee/beer-if-you're-not-baptist/tea-if-you're-English, answering questions, praying with them, and just hanging out with them. Most of your time is spent being you with your church. If people have voluntarily said they want you to be their real-life pastor, do you think they want you to put on an act on Sunday morning? Even if they did, they would come to grips with the false reality at some point.
This is not to say there are not preaching and communication principles you can learn and imitate from your favorite preachers. It is simply to say that as you learn the principles of preaching and communication, you should execute them with your own unique voice, mannerisms, and style. God does not want John Piper to pastor your church. He does not want Jack Graham in your pulpit. He is not bummed that there is only one Matt Chandler. He called you because He wants you to pastor your flock.
Be yourself. Be yourself as you prepare your sermon. Be yourself as you walk to your pulpit or table or stool. Be the guy who got coffee with that student on Tuesday, held a staff meeting on Thursday, and consoled the woman who just lost her husband on Saturday. Be yourself because you got called.