The overall plan

The plan of happiness, the plan of redemption, and the plan of mercy are all parts of the same plan.  The plan of happiness says that “if it were possible that our first parents could have gone forth and partaken of the tree of life they would have been forever miserable, having no preparatory state, and thus the plan of redemption would have been frustrated.” (Alma 12:26)

If they had partaken of the tree of life after having partaken of the tree of knowledge, therefore knowing good from evil they could never die. They/we would be forever miserable in this world in our sins and could never return home.

“And now the plan of mercy could not be brought about except an atonement should be made, therefore God himself atoned for the sins of the world to bring about the plan of mercy.” (Alma 42:15)

We had to have a way to cleanse ourselves or to repent, but “repentance could not come unto man except there were a punishment”….now how could a man repent except that he sin? How could he sin except there were a law? And how could there be a law save there was a punishment?” (Alma 42: 15-17)