I would like to ask for a possible classification of the following philosophical positions:
Everything is a simple result of natural occurances and as such lacks any objective value. Even if a god existed and created us with a purpose in mind, that would still not give meaning to our lives. What gives meaning to the purpose for which our creator created us? (Think the Rick and Morty episode where Rick creates a small universe in order for the life forms in it to power his car).
Humans are just very good biological learning machines. Our values and ethics are a result of natural selection and are passed into the next generation in part because of genes and in part because of parents driving and assisting their childrens' association process when young. Morals are relative and non-objective and just widely widespread.
All human actions are driven by personal satisfaction (even "altruists", are altruists because in the end they gain more personal satisfaction by acting altruistically compared to the alternatives, mothers gain personal satisfaction by caring for their babies etc.)
There is no inherit meaning in living but attempting to find and/or give meaning to our lives is a widespread cultural characteristic not necessarily inherit to us as a species. Therefore, a human can live happily by acknowledging that their lives has no meaning, that is, if they don't value life having an objective meaning.