Your polluted self (nafs -corrupted soul) has to purify (self realize) itself to reach the pure existence of its consciousness (Heaven)

Your past Karma, present skills (Good and bad) and your regrets (thoughts) decide your next incarnation(s)

Therefore use your Free Will

Not to demote but to promote your soul from bitter to better

I (God) will reduce you to apes and pigs – Quran 5.60
I (God) will demote you to a panting dog – Quran 7.176

Death is a bridge which unite friend to friend – Imam Gazzali

Death(s) and birth(s) are bridge(s) which unites similar energies – Azgar – Sufi author