"We win or we learn." Try to win more than you learn over time.

https://en.wikipedia.org/wiki/Bible

https://en.wikipedia.org/wiki/Tao_Te_Ching

https://en.wikipedia.org/wiki/Quran

Critical thinking skills are the most essential tools, so is studying philosophy. You have agency, use it.

Of course you could always abdicate your agency to religion (pick one), or politicians, or influencers, or money/consumerism.

No matter how you dice it, the choice is always yours, and yours only,

    mySelf = Human.new()
    defer mySelf.recycle
    while myself.not_yet_dead():
        mySelf.improve()

Pali canon are also a personal favourite. Tao te ching is similarly good.

I havent read the bhagavad gita or the upanishads, but I should do so.

The reality here is that there's a single uncaused God. Even the polytheistic Hindus believe there's only 1 uncaused God(Brahman). But this God is too complex for human understanding. The religions are all bad, very insufficient, explanations of the God with a cultural lens to help in that understanding.

Your importance of your operating manual is to get you to the point that you live at peace with your neighbours and even your enemies. Life is too short to have enemies. Which is then complex about how to avoid ending up with enemies because cultural differences can be the break. Which is the importance of multiple religions.

   —Monty Python, 1983