When our bodies are resting, the mind tends to get extra active. It's important to stress - there is nothing wrong with thinking. Thinking can be helpful, constructive, creative, imaginative. What we might want to manage is the tendency to go into loops with thoughts, and be unable to break away from that loop. Here are a few strategies you can use to quiet down the mind while practicing this pose, or any other time in your life. Essentially, we want to allow the mind something else it can do, for example:
1. Count your breaths, and start back at one when you lost count :)
2. Use the time in the pose for a gratitude practice, becoming aware of people, events, things, experiences that you are thankful for
3. Use the time in the pose for your meditation practice
4. Pay attention as the breath flows in and out of the body - what do you notice physically and emotionally with every inhalation and exhalation?
5. Enjoy music that you like in the background
And if all this fails? Think! Make to-do lists, engage in memories or future plans. It's not forbidden. Only, try to make it a choice.