Musar zu Jechezkiel 18:13

And with interest and usury, there is a negative commandment - as it is stated (Leviticus 25:36), “Do not exact from him usury or accrued interest, but fear your God” - and it is rectified by a positive commandment, as it is stated, (Leviticus 25:36) “let him live by your side as your kinsman.” Its explanation is, if you have taken interest or usury from him, surely return it to your brother, in order that he may live with you. And his punishment is very weighty - so long as he does not fix that which is crooked, he does not come to the resurrection of the dead, as it is stated (Ezekiel 18:13), “He has lent with usury, or exacted accrued interest - shall he live; he shall not live!” And our Rabbis, may their memory be blessed, explained (Pirkei De’Rabbi Natan 33), it [to be] about the matter of the resurrection of the dead. And our Rabbis, may their memory be blessed, said (Exodus Rabbah 31:6), “Anyone who has the iniquity of interest in his hands will not have an angel intervene (teach) merit on his behalf.” And this is [the understanding] of that which, “shall he live,” is stated as an expression of question and wonder - is there an intervener that will say that his case is to live? All of them will answer, “He shall not live.”

How much more so for the sin of taking interest, which is considered as great as denying the G-d of Israel, G-d forbid. Our sages of blessed memory commented on the verse: "he has loaned on interest; and has taken increase; shall he then live? He shall not live! [He has done all these abominations; he shall surely die; his blood shall be on him]" (Yechezkel 18:13) - '"he shall not live" refers to living in the time of the resurrection of the dead for he and his dust are abominable and detestable in the eyes of G-d' (Shemot Raba 31:6). I do not see a need to elaborate on this for its dread is already imprinted on every man of Israel.

However, the factors which cause loss of this trait are all those detriments to the trait of Watchfulness, in addition to lack of proficiency in knowledge of the laws and ethics (Mussarim) as I wrote above. Our sages already stated: "an ignorant man cannot be pious" (Avot 2:5). For one who does not know cannot possibly do. Likewise they taught "great is study in that it brings one to doing" (Kidushin 40b).