Abusing the gift of forgetfulness

דברים לב:יח 

צוּר יְלָדְךָ, תֶּשִׁי;  וַתִּשְׁכַּח, אֵל מְחֹלְלֶךָ

 Devarim 32:18 

God has granted you the ability to forget, but you have forgotten God himself

Forgetfulness is a gift. Were we to remember every detail of our lives, we would be unable to function efficiently. We would be constantly torn by sorrow and grief, eaten away by guilt, and weighed down with responsibility. In Parashat Ha'azinu, however, Moshe Rabbenu complains that we abused this gift and forgot our Creator who provided it to us in the first place.

The Maggid Midovno illustrates this with the following mashal, which my father likes to share from time to time:

In a time before credit scores and collection agencies, there lived a man who was deep in debt. Unable to pay back his loans, he turned to a friend for help.
"Just feign insanity and they'll leave you alone," his friend advised. "When they come to collect their money, start singing as loud as you can. Your debtors will think you've lost your mind and they'll leave you alone."
That night, an angry mob banged on his door.
"Where's our money?!" They shouted at him.
Bearing in mind what his friend told him earlier, he broke out in song: "LALALALALALALA!"
His debtors concluded that the stress must have addled his brain and abandoned hope of getting their money back.
Later that year, short on cash once more, this man turned to his friend, who had advised him earlier, for some money. He promised profusely that he will repay the loan in a timely fashion. The friend reluctantly handed over $100.
A week passed, and then another. There was no sign of the debtor or the $100 that he owed. Upset, the friend knocked on his door a few days later, hoping to get his money back.
As soon as the man saw his friend by the door, he broke out into song: "LALALALALALALA!"
"Idiot!" his (former) friend shouted. "I taught you that trick! You can't use it against me!"

Hashem graced us with the gift of forgetfulness, but sometimes, as the pasuk attests, we use it against Him and forget Him and His grace.