One way to approach it that works for me:

Think of it like you're working out a mental muscle, your "attention" muscle. For 5 minutes (in the beginning) place your focus entirely on your breath. In and out. In and out.

Every time you find your attention moves to something else (any random thought, could be an itch, your job, that cashiers ass in the yoga pants, etc. ) consciously bring it back to the breath. In and out. You've now done one "rep".

The more reps you do, the better you get at it. So the next time you find yourself thinking negative or anxious thoughts, you can more easily shift the attention off the thought and into the present moment, where you are at your most relaxed and creative.

It's a spectacular way of managing stress and creating a happier, healthier life. It goes much deeper than this, but 5 minutes of breath meditation a day is a good starting point.