«And among those nations you shall find no rest, nor shall the sole of your foot have a resting place; but there the Lord will give you a trembling heart, failing eyes, and anguish of soul» (Deuteronomy 28:65).
A lack of peace, along with fear, weariness, and sorrow are part of the list of punishments for the disobedient that we find in Deuteronomy 28. The idea was to impress the minds of the Israelites with the dangers of distancing oneself from the pact. Each warning is a natural consequence of disobedience. Those who did not serve God voluntarily would arbitrarily serve enemy nations. If they did not fear God, they would fear plagues and pandemics. If they did not submit voluntarily to God, they would be subdued by enemies. These warnings were fulfilled when Israel was conquered, first by the Babylonians and later by the Romans. They were dispersed and exiled among different nations as captives. Even today, cruelty, abuse, kidnappings and murders, wars, illnesses, famines, pandemics, and such things are the result of having disobeyed God. In reality, they are all consequences of sin entering into the world because of human disobedience.
When our relationship with God is broken, the promised blessings disappear. You were created to serve and worship God. Abandoning that purpose is losing the purpose of your life, and you will feel empty, sad, anguished, and fearful. Fear can be because of either real or imaginary threats, as described in Deuteronomy 28:66: «Your life shall hang in doubt before you; you shall fear day and night and have no assurance of life.» «The sinner’s own thoughts are his accusers; and there can be no torture keener than the stings of a guilty conscience, which give him no rest day nor night.”- The Desire of Ages, ch. 22, p. 223. But do not despair. «But from there you will seek the Lord your God, and you will find Him if you seek Him with all your heart and with all your soul. When you are in distress, and all these things come upon you in the latter days, when you turn to the Lord your God and obey His voice (for the Lord your God is a merciful God), He will not forsake you nor destroy you, nor forget the covenant of your fathers which He swore to them» (Deuteronomy 4:29—31).