If you've ever been in one of my classes you've heard it many times and yet it's still a challenge to simply "be in the moment" and not anticipate the next. In our culture we are extremely preoccupied with where we are going, what's coming next. Being completely present exactly where we are takes a great deal of concentration and practice. The next time you're in class, observe your natural tendencies in each pose. Are you always arriving in a pose ahead of the breath or instructor's cue? Are you always rushing the pose and breaking it down to move on before you've really felt anything in it or been instructed to move on?
You've taken the time come to a "guided yoga class", try putting your patience and your trust in your yoga instructor and moving when and where they instruct you (obviously using any modifications you need.) Let go of anticipation and expectation and allow yourself to be led safely through the experience so you can FEEL EVERYTHING.
Even though you know where you're going, be where you are...and enjoy.