Some Christian preachers teach: “You should not meditate (in the sense of eastern religions), because a part of meditation act is not-to-think.”

I doubt this:

(Matthew 24:44) “Therefore be ye also ready: for in such an hour as ye think not the Son of man cometh.”

(Luke 12:40) “Be ye therefore ready also: for the Son of man cometh at an hour when ye think not.”

Jesus comes to us when you do not think! Maybe we should not follow eastern religions in how to meditate, but we should sometimes not to think, so that Jesus to come to us.