I think in the spirit world (after our physical death) that we can access every life we have lived and this access is as emotionally real as if we were back in the physical. Most spirits re-live emotionally the happiest life or point in that life.
The reason we choose to be reincarnated to the physical and loose our lives knowledge is because we began to miss the physical. We began to miss the mystery, fear, danger, challenge and pain. From this the physical begins to look more attractive because through the physical we can experience more levels of existence and we make the choice to die in the spiritual relationship with GOD and be reborn in the physical relationship with GOD and we continue this cycle until we recognize the Supreme Being at which point we become Servants of the Supreme Being but even steal we continue to have to return to the physical.
Just my personal invention and suspicion.
Peace.