It's clear to me that the critical decision governing one's behavior in life is belief in God and the afterlife. All other beliefs and subsequent actions stem from this root decision.
Peace be upon you
Click on any word in the image below to see a verse from the Quran about that word.
Every soul will have a taste of death, and you will receive your recompense on the Day of Resurrection. Whoever is swayed from the Fire, and admitted to Paradise, has won. The life of this world is merely enjoyment of delusion. [3:185]
I have not created the jinn and the humans except to worship Me.[51:56]