The above said stanza clearly states that if you are inclined to laziness, inertia, do not do your daily duty & just becomes careless about your life, then you are falling a pray to "Tamas" or "TamoGun". A person falls a pray to "TamoGun" due to his/her ignorance & delusion only which causes indolence, laziness and sleep.
Bhagwat Gita illustrates the "Tamas" or "TamoGun" very clearly & beautifully. As per Bhagwat Gita this Material nature consists of three modes i.e. Sattva, Rajas & Tamas. Out of the three modes of Nature, "Tamas" or "Tamo Gunn" is the one which is responsible for ignorance, delusion, indolence, laziness and sleep. We should not fall a pray to this "TamoGun". We should do our daily duty, coming out of this laziness and sleep, which are born of ignorance. Below are verses of Bhagwat Gita which explains about the qualities of this "TamoGun".
"sattvam rajas tama iti
dehe dehinam avyayam" (Bhagwat Gita: Chapter Fourteen verse 5)
"Sri Krishna said: O Arjuna, Material nature consists of three modes—Sattva (goodness), Rajas (passion) and Tamas (ignorance). When the eternal living entity comes in contact with nature, he becomes conditioned by these three modes."
"tamas tv ajnana-jam viddhi
tan nibadhnati bharata" (Bhagwat Gita: Chapter Fourteen verse 8)
"Sri Krishna said: O Arjuna, know that "Tamas"- the mode of darkness, born of ignorance, creates delusion in all embodied living entities. The results of this mode are madness, indolence and sleep, which bind the conditioned soul."
"aprakaso ’pravrttis cha
pramado moha eva cha
tamasy etani jayante
vivrddhe kuru-nandana" (Bhagwat Gita: Chapter Fourteen verse 13)
"Sri Krishna said: O Arjuna, When there is an increase in "Tamas"- the mode of ignorance, then darkness, inertia, madness and illusion are manifested."
sattvikam nirmalam phalam
rajasas tu phalam duhkham
ajnanam tamasah phalam" (Bhagwat Gita: Chapter Fourteen verse 16)
"Sri Krishna said: O Arjuna, The result of pious action is pure and is said to be in the mode of goodness. But action done in the mode of passion results in misery, and action performed in "Tamas"- the mode of ignorance results in foolishness."
"rajas tamas chabhibhuya
sattvam bhavati bharata
rajah sattvam tamas chaiva
tamah sattvam rajas tatha" (Bhagwat Gita: Chapter Fourteen verse 10)
"Sri Krishna said: O Arjuna, Sometimes the mode of goodness becomes prominent, defeating the modes of passion and ignorance. Sometimes the mode of passion defeats goodness and ignorance, and at other times "Tamas"/Ignorance defeats goodness and passion. In this way there is always competition for supremacy."
Pl. note that all those people who have a destructive way of life, like those terrorists who struck in Mumbai, killing people mercilessly, were in fact under the influence of "Tamas" or "TamoGun", as their mind & intellect were covered with ignorance due to Tamasic nature. Hence their perverted mind thought that killing the innocent people was their duty, while they were doing demonical work only by doing such killings.
In fact "TamoGun" engulfs one's mind & intellect with the darkness of ignorance & makes a person believe that, whatever, wrong he/she is doing is right, while it is their perverted thinking only which make them do wrong only, the consequence of which shall be misery only in future. So we should not fall a pray to Tamasic nature & should not do devilish acts which lead one's soul to degradation only. To read more about the qualities of people of 'Demoniac Nature' who are under the influence of "TamoGun", read my earlier Blog Post here.......................Qualities of People of 'Demoniac Nature'.