دَسَّاهَا (instills): Instilling is to hide something in something else. Allah (swt) says:

  {أَمْ يَدُسُّهُ فِي التُّرَابِ ۗ أَلَا سَاءَ مَا يَحْكُمُونَ }

(or bury it in the ground? Unquestionably, evil is what they decide.) (An-Nahl: 59)

(In this verse the same Arabic word but in present tense is used to mean: to hide him in the ground).

Hence, he instills his soul in sins, wrongdoings and in the pitfall astray. He humiliates his soul, seduce it and makes it away from obedience, purity and goodness. Consequently, he finds but the loss and failure.