The thoughts that arise as obstructions to that are from impressions.
In plain words: Thoughts that block this freedom come from old impressions left in the mind. The teacher explains that these are ideas that we need outside things to be happy, and they must work themselves out.
All the various ideas that arise, making us believe that we require something external to make us happy, are obstructions to that perfection. The Purusha is happiness and blessedness by its own nature. But that knowledge is covered over by past impressions. These impressions have to work themselves out.
Namaste.
A calm guide to life, the mind and the old teachings.