The soul and the body

As the "the thought force and the animal force are partners," as described by 'Abdu'l-Bahá, the soul learns and works through the intermediary of the body. That means that the growth of religion and civilization has been what has been driven the growth and development of the human brain, and that also what we are capable of learning as souls is directly limited to what our brains can do.

Several studies have shown that people from different cultures use different parts of their brains, sometimes even when approaching the same task! So there are massive amounts we can learn about what it means to be human simply by interacting with people of other cultures. Trying to do it ourselves would be like trying to reinvent their entire culture which took thousands of years to form.

And while "spirit has no gender," and there is no "giving and taking in marriage" in "the next world", because our brains form differently depending on whether estrogen or testosterone is present in the body, there are distinct spiritual qualities that both women and men will have in both this world and the next, and need to be developed here. People who are afraid of being abused or being unwanted are unable to fully enjoy and thus learn from the experience, people who are in cohabitating relationships are ninety-one times more likely to abuse their partners than married couples so there is a strong relationship between love and commitment, polygamy leads to the oppression of ones' spouses, and thus that part of a soul's learning can only happen within a monogamous marriage. Sexual activity also stimulates the production of both of those hormones, so monasticism is not ideal.

And anywhere we can learn more about how to think we should, most particularly by doing things, because otherwise we are only theorizing or fantasizing and our work will be slow and possibly wrong. This is why "work done in the spirit of service is the highest form of worship."

There are many more applications to this, but I am not prepared to write about them.

Some studies have found that doing a lot of learning, which also occurs when making decisions, takes energy from the brain to accomplish, and as such the brain can become 'tired.' I believe this is the physical manifestation of what is described in this verse:

Recite ye the verses of God every morn and
eventide. Whoso faileth to recite them hath not been
faithful to the Covenant of God and His Testament,
and whoso turneth away from these holy verses in this
Day is of those who throughout eternity have turned
away from God. Fear ye God, O My servants, one and
all. Pride not yourselves on much reading of the verses
or on a multitude of pious acts by night and day; for
were a man to read a single verse with joy and radiance
it would be better for him than to read with lassitude
all the Holy Books of God, the Help in Peril, the Self-Subsisting.
Read ye the sacred verses in such measure
that ye be not overcome by languor and despondency.
Lay not upon your souls that which will weary them
and weigh them down, but rather what will lighten
and uplift them, so that they may soar on the wings of
the Divine verses towards the Dawning-place of His
manifest signs; this will draw you nearer to God, did ye
but comprehend.

Bahá'u'lláh, The Kitáb-i-Aqdas, p. 73

It is easier to learn things when in social settings, especially the larger, more diverse, and united the group is, because the mind can easily weigh a decision in terms of the social cues from everyone around them, while making decisions alone a person can even forget about the importance of other people and making decisions becomes very difficult and learning increasingly impossible the longer one spends alone. I believe this is what meant by the fact that "the spirit of man withers in isolation." Also, I think the more socially capable the person is the more you can learn from and reference them, which I believe is what is meant by the verse "he that seeketh to commune with God, let him betake himself to the companionship of His loved ones."

So, some people have a hard time getting to sleep at night even though they were moderately physically active during the day; this is probably a sign of an underused mind. Because the brain, driven by the soul, is like a growing child in that it is continually learning and developing, it feels restless when it is not able to exercise and jump up and down.

And some people can be perpetually tired because they want to learn more than they are able too, an effect that decreases in social settings because of the input described above.