Those aren’t operating manuals, and two of them basically sum up to “if the troubleshooting guide doesn’t work, wait till tech support is back in the office”. At least in the Vedas there’s a bit of a nod to “have you tried powering it off and on again?”.
Mine is called the Bible. Which is a greek word for "the books" but commonly understood to be "the holy scriptures'. I'm happy to include Quran and Book of Mormon and all gnostic gospels into this mix; it's not important for this discussion.
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.
Believe it or not, human beings aren't teleologically designed; and the future is not knowable (even though some things are broadly predictable — as far as we know). (See the problem of inference / black swan problem, to start.) So no one knows for sure (in general or in your, or anyone else's, specific case).
Best we can do is heuristics, rules of thumb, etc.: ancestral wisdom based on as much time and experience as possible. Included in those — and among the most useful and reliable — are tips, not for maximizing benefits/successes, but for avoiding almost certain misfortune and ruin.
Hence: avoid harmful substances and behaviors (alcohol, drugs, gambling …); generally avoid/neutralize envy, greed, etc.; avoid killing; teach yourself contentment / how to live with life's basics / how to want what you have instead of trying to get what you want; keep an inner score card instead of a worldly, external one; care for the body; be charitable; beware tampering with complex natural systems (Chesterton's Fence); eschew superfluity; focus on process more than outcomes (what is in your control, not what is outside of it); etc.
Take care of your downside risk, and then acquire free options / expose yourself to positive expected-value uncertainty.
Everyone's manual is built upon their lived experience, and only parts of each manual would apply to others. You are building your manual through your experience to become the best version of you one day at a time. Take that which is value from which you observe and are taught by others, discard that which has no value or does not apply in your context.
"We win or we learn." Try to win more than you learn over time.
I guess because various people believe different thing will happen to them when their life ends. The question is- which of those options (on what happens when life ends) is truly what's going to happen. Surely, if Bible is true you want to live such life so you are not ending up in hell, if Quran is true you do whatever it says to maximise the outcome, same for Hindu, Budha, and of course Atheism. I study this to have strong grounding on how to live, and there is scientiffic method to do this, though it requires time and effort.
Many colleges and universities have courses on The Good Life taught with different perspectives. Here's one - a YouTube version of the most popular course ever at Yale University - with a focus on psychology:
We don’t know much about human minds. In additional, we don’t follow manuals. The brain doesn’t really always listen to our will. TBH I’d very much hope that I’m a machine that can devote to a single thing for an undetermined amount of time, never have burnout and can immediately context switch with minimum effort. But I’m not made of that.
Well, first, there are a number of different operating manuals, as already mentioned in the comments.
But why is there not a single operating manual? Because the world is composed of vastly different cultures with their own values, norms, and religions and they have different ideas of how the best version of the self is defined.
Why? Because we evolved, we weren't manufactured. WRT how to become the "best" version of ourselves, that depends entirely on how you define "best", and there's no universal agreement on that. That's why so many different "manuals" are available.
There's actually plenty. Aristotle and Plato basically dedicated their life to it. In an ever changing word is hard to write set rules, outside of morality.
I was thinking the same. Immediately, the "Enchiridion" of Epictetus came to mind. It's also called "The Manual", which is basically a guide to living life from a Stoic perspective. As others have wrote, there are lots of manuals. Maybe too many.
Uh, try and be nice to people, avoid eating fat, read a good book every now and then, get some walking in, and try and live together in peace and harmony with people of all creeds and nations, and, finally, here are some completely gratuitous pictures of penises to annoy the censors and to hopefully spark some sort of controversy, which, it seems, is the only way, these days, to get the jaded, video-sated public off their fucking arses and back in the sodding cinema. Family entertainment bollocks. What they want is filth: people doing things to each other with chainsaws during tupperware parties, babysitters being stabbed with knitting needles by gay presidential candidates, vigilante groups strangling chickens, armed bands of theatre critics exterminating mutant goats-- Where's the fun in pictures? Oh, well, there we are. Here's the theme music. Goodnight.
https://en.wikipedia.org/wiki/Bible
https://en.wikipedia.org/wiki/Tao_Te_Ching
https://en.wikipedia.org/wiki/Quran