Despite our trials, God is still a just God. In the pre-mortal existence, we were all given "informed consent". Informed Consent is what a medical doctor does before doing a painful surgery or procedure. Similarly, in the pre-mortal existence, we were fully made aware of the potential for suffering here on Earth but also the unspeakable rewards. Also, God promised to make up to us all of our losses. The Bible reveals that not only did we accept the terms, "we shouted for joy!".
The reality of the pre-existence and informed consent is critical to the justice of God. Denying this doctrine Christian churches have lost ground and many souls to atheism on this very issue.
Job 38:7 When the morning stars sang together, and all the sons of God shouted for joy?