For children, - Regretting on the Day of Judgment in Hereafter (Akhirah) for not following Deen-e-Islam

Once, a group of people were traveling on rocks at night. A voice came
from the sky that whosoever picks up the rocks will regret and
whosoever doesn't pick up the rocks will regret. Now, the people were
confused. How can this be? Whether you pick up the rocks or not, you
will regret!
Anyway, some people picked up the rocks and some didn't. In the
morning when they reached their homes, they saw that the rocks turned
into diamonds. Now, those people who didn't pick up the rocks started
regretting saying, "If only we had picked up some rocks." Those people
who did pick some rocks also started regretting saying, "Why didn't we
pick up more rocks?" Both sides ended up regretting.
Dear Muslims, this same incident will take place with us on the Day of
Judgment. Those people who spent their time in useless things will
start regretting by looking at those who achieved a great position in
Paradise by spending their time in the way of Allah (SWT). Now, those
who did achieve a position in Paradise will start regretting by
looking at those who did more than them and are higher in status.
"Alas! If we had only done more to please Allah (SWT)."
Allah (SWT), the Majestic said: "And could you but see when the guilty
shall hang down their heads before their Lord: Our Lord! We have seen
and we have heard, therefore send us back, we will do good; surely
(now) we are certain." Noble Qur'an (32:12)
Imam Sadiq (as)said: All evil is placed in a house and its key is love
for this world. All good is placed in a house and its key is
abstinence in this world.