'Nothing to be attained' is the all-important theme of the Sutra. The obstruction alluded to in the above sentence refers to the three obstructions of function, to wit: 1) the karmic obstruction, or the obstruction of deeds done in the past; 2) the obstruction of retribution; 3) the obstruction of passion.
The above quote implies that the supramundane Void is the True Existence of all dharmas, and for that same reason no dharmas can be obtained. Since the Bodhisattva cannot seek outside help when dealing with obstructions, he has to rely on insights provided by his own radiant wisdom for his attainment of freedom. The first to be eliminated is the obstruction of retribution, which is of two kinds: the dependent condition (oneís circumstances) and the resultant person (oneís physical condition). The Bodhisattva has already discarded these two kinds of obstruction, and the different sorts of anxiety have all vanished from his mind.