you are right but the tale still works no matter the sophistry a reader may be willing to use

No assumption here, a book by itself can never hold such amount of content and is really a shortcut. What I in fact supposed is that you are already a pantagruel of books and so, you are on your way to do what I mentioned but I still wrote the post because that's one of the things that people do when they are bored during the weekend.

You can ponder about my intentions as much as you want but it just draw my attention such a high expectation from a book, "a really comprehensive history of humanity... with a lot more detail and depth" is (or could become) a lifelong aspiration, not something to digest in a few hours.

"Distructive" discurse, if it is done properly, may be as fruitful and rewarding as the other one. It cleans the land and you can start to build something without impediments if that's what you want. I think it is better not to do it and spend that energy trying to survive the cold winds but I have nothing to say (more precisely, no energy to spend) against those who feel that they need a house no matter what

Indeed... but there is a third kind of people, those who don't talk, just think.

Effort adds value to everyting, we both agree, but what is mundane, what is accomplishment... for you and me, could be defined in a very different way by other people (and guess what, they would be right)

No matter how much you search or read, not even in 100 lifetimes you will get "a really comprehensive history of humanity, from its earliest beginnings to modernity... with a lot more detail and depth" but, taken as a whole, that's a project worthwhile to undertake during the time you have on this planet. If you read everything, from Chinese classical poetry to tweets and anything in between, and you do it in the proper way, (thinking as best as possible every time) you will then have the book you are searching for.

find then a bon-vivant, a sybarite, a pornographer... and tell them that their sensual pleasures will "eventually wear thin" (when they die will be so, sure, but they have plenty to enjoy meanwhile).

The question of the youngster here (the main thing under discussion) was more or less "if I am going to die, why I was born" (Ionesco) The answer is within himself, not written here or in any other place and it is not something to be done as you and Bitter Crank say, a kind of task or homework that you do and, voilá, you find the purpose of your life. If that's the solution, the film "Soul" has done a heck of a better job than you guys. He just logged into a phylosophy forum and asked a +30000 years old question with no answer. Do I need to explain further what's going on here?

Well, you could also say that people learn what is difficult because they are wise, it works both ways. Yes, we all have pros and cons and this person is trying to figure them out, I don't think his problem is knowing how to use his gifts for the collective good.
Your last equation doesn't work in real life, I can eat chocolate, have sex, have a drink... and get lots and lots of pleasure with little or no effort.

OK, one won't find the solution but could at least start to figure out how to tackle this kind of problems by discussing about them with others, I guess we both agree about this and I also share with you the good intentions. Your reasoning is of course correct but in the real world we both know the fate of saying to people "don't do this, do the opposite".

A good idea indeed but...wait... isn't he now asking for help from others in order to improve himself? Is this as simple for him as turning the screwdriver to the left because he is pushing to the right?

A good illustration for what you have said because your reasoning is as circular as that one at the center (or the bigger ones created by the arrows) but I am afraid this person is not here in search of circles, he wants lines as straight as possible. You'd better show them here if you have them (not me)

The idea of goals in a life that has "issues until you drop dead" is too vague. There are worthwhile actions rather than goals, at least they are much more concrete, something to work on. Not very encouraging anyway to say "become Sisyphus and you'll feel better", "jump into a goal and it will take care of your existential problems"... or whatever you had in mind. People sometimes makes everything more complicated than it is and sometimes simpler than it should be. What you said is in the second group.

No need to dissolve human life into the universe. Life doesn't have a purpose but this emptiness creates the room within itself for it (is "purposeable", if you let me use bad language) Once you find it, you never ever tell anybody that your life has no purpose.

As for your final paragraph, telling a youngster "be a good and reasonable old man" (like yourself, at least that's what looks like) won't work and you already know it. The good wishes embedded in those words at least are something worthwhile but usually they don't work either.