My highest power has stated to me:

"As one starts their journey from soul to soul with a body [and back again, and so on and so on], you generally have easy lives. When you return to source/heaven/god after every lifetime, you will be given a choice to stay in that realm that you are put in or to go back to the master class [Earth]to attain a higher level. ...It is around this time where you the soul and collectively the community of spirits start to decide what level they want to attain and what price it will cost them on earth. [No pain, no gain]. Now you can understand that not everyone wants to attain nirvana as you say.

To attain nirvana, you would go on a completely different cycle, and that usually happens after a vast number of lifetimes lived. The lifetimes that you start to choose to live [at that point] are with great suffering. Think of the severely retarded, the severely mentally ill, POWs, people who have died violently at the hands of great evil and even stillborns who give up their life experience for the host."