The nature of meditation
It is the nature of meditation to become creative. In order to capture the flavor of creation our thoughts while being directed cannot be forced into a mold that would not be natural to their expression. This is apparently a paradox. How can we both direct our thoughts and yet let them go.
Here the answer is simple. We direct the arrow and then let it go to reach its mark.
One of the adjuncts of meditation is that our thoughts will open their expressions in response to our feelings of approval during the ongoing process. These feelings of approval provide the certainty of preparing the way before us.
Just like we don't wear the same clothes each day we also do not have to try and copy each day's meditation. We may use as a framework exercises to regulate our breathing but our inner game must always be determined by inspiration.