I truly believe an average life, were neither terrible disease nor tragic injustice strikes
already offers what our aims are;
in a simple sentence: we are almost perfectly tuned to our biology and feelings.
On the other hand each one of us will develop his or hers own desires, like
playing on a stage behind a Steinway grand piano, or revolving high in the sky
around our little planet and snapping pictures, or just raising up wonderful kids
with his loved one.
All in all my answer is: to realize at least some of our carefully planned projects.
I purposely don't use the word 'dream' as those will just stay dreams, if a good plan
does not follow.
Too simple? Sorry, sometimes this is a propriety of truth!
Let me try to reverse the logic, if you did not fall asleep.
If a common dream (out of Nature or biology boundaries) or aim was for all and each of us, fulfilling that dream could easily turn into an horrible nightmare of struggle, violence and maybe even war: the fact that our plans and desires are so different is a lucky circumstance,
and an important vaccine against evil ruling the same little planet previously cited.