אם בחקתי תלכו ואת מצותי תשמרו ועשיתם אותם
26:3 If you follow My decrees observe (or guard) my commandments and do themOn the other hand, the curses start ou
ואם לא תשמעו לי ולא תעשו את כל המצות האלה
ואם בחקתי תמאסו ואם את משפטי תנעל נפשכם לבלתי עשות את כל מצותי להפרכם את בריתי
26:14 If you will not listen (refuse to listen is the implication) to Me, and you will not do all these commandments
26:15 If you will despise My decrees and your souls reject (lock out) My laws, in order to (deliberately) not do all My commandments, so that you annul My covenant.
As we see, the blessings and the cursesw come about because of a set of deliberate actions. It is not that a person is "happening" to act in a certain way or is negligent or "forgettiing", but that a person must explicitly decide what path to go on. The original people who rejected Hashem explicitly decided that they would go against the commandments of the Torah and would refuse to listen to Hashem. People would not eat nonkosher food because it happened to be cheaper or was available, but would deliberately buy nonKosher food even when Kosher food was available. The Socialist Workers would deliberately schedule their dinner/dance for Yom Kippur. THis is what causes the curses to start.
Later on, once they have brought the curses on themselves, we see that continuing to act with "indifference" (בקרי) will cause the curses to continue. Once someone has started down the wrong path, it takes a positive action to break away and return to the right path. This is the tragedy of the descendants of those who started the breakaway cults. They are raised in the mistakes of their anscestors and no longer know what they must do to stop the curses that their forebears have left them and return to the blessings that are their heritage.
Their is a statement attributed to a soldier in the Yom Kippur War
"My father knew how to pray and refused to do so. I want to pray but do not know how to"This is what we need to learn how to do in order to regain the blessings that are our heritage.