While studying 2 Corinthians 10:5* today, I was reminded of a talk President Packer gave years ago in general conference which was turned into a filmstrip and shown to the youth of the church. The idea that I can have control over my thoughts, along with a tool to help me succeed in that, has stuck with me ever since, and has been of great benefit to me. In the hope that it might be of benefit to you as well, here's a small collection of internet resources for the talk.
The original talk - October 1973 General Conference
A condensed version - April 2008 New Era
And a YouTube creation of the original filmstrip - Worthy Music, Worthy Thoughts
*"Bringing into captivity every thought to the obedience of Christ."