Abba wrote: "I do believe this world is very good, we can only do mitzvot and teshuva here, not in Gan Eden. Then why do I have a feeling that I would never want to come back here in a reincarnation? I should want to come back, but I don't." 

Gutman: Abba is referring to the "upper Garden of Eden," a completely spiritual place where the soul goes after one passes from this world. Now we are in the Lower Garden where we have to do the work, and then we pass on into the Upper Garden.

     If we live a good life, a life of kindness and fulfilling the commandments, then in the long run, it is much better to have come here. Being here will improve our future forever. But the fact is, there are no problems in the Upper Gan Eden, so who would want to leave it!

     The Ethics of Our Fathers expresses it this way: "A single moment of repentance and good deeds in this world is greater than all of the world to come. And a single moment of bliss in the world to come is greater than all of this world."