Anchoring refers to the process of associating an internal response with some external (or even internal) stimulus so that the response may be quickly and sometimes covertly, but always automatically, triggered.
Try it for yourself. Think of something that makes you feel really, really good, and as the good feeling starts to build, just squeeze together any finger and the thumb of your non-dominant hand. Add in your favorite song and turn the volume up in your head to the volume that makes you feel really good. Now take that feeling and double it in size and then double it in size again, all the time keeping your finger and thumb together. Now, release your finger and thumb and repeat those exact same steps a few more times until simply squeezing together your finger and thumb makes you feel really good. Cool, eh?