we always meditate and talk about the things we love.
I love my job, I constantly work on my job and try to make it better.
I love money, I constantly meditate and talk about how to make money.
I love my car, I constantly discuss about cars and the quality of my car.
I love my wife and family, I constantly meditate and serve my family.
Therefore, this is a natural process.
Similarly, if we love Krishna, then constantly we will meditate, serve and talk about Krishna thus fulfilling Mahaprabhu's prayer of "yare deko tare kaho Krishna upadesh".
This is preaching. Therefore preaching is but a natural output of one's love for Krishna.