Friendship is a completely alien phenomenon to me, too, and that definition might explain why.
There are some things almost anyone has always been able to count on me for: borrowing my class notes; "help" with homework; having me do the lion's share of any group task; having me spend as much time as needed to help them with something, with no regard for the trouble I'd get into when I had no time left for something else; "borrowing" stuff with no intention of ever handing it back to me, and, when I ask for it, acting like I'm funny in the head; physically beating me if they feel like it,.... Generally anything that means using me as their b***h.
There are other things noöne's ever been able to count on me for: fighting aggressors, and especially succeeding at defending myself or others from them; defending our case if the fight happens anyway and it's halted by some authority; being worth my salt as a teammate playing any sports; anything involving social skills.
So why be my friend when anything useful I might have to offer, you can take by force, with no need to let me count on you, and anything that helps the group as a whole get respect, I can't be counted on for?
In sum, to have true friends, it is necessary---though by no means sufficient---to be both strong and brave.
I think some would say only the latter matters, but, if you're weak and brave, you won't last long, so you'll be dead before anyone can be your friend.
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The red lake has been forgotten. A dust devil stuns you long enough to shroud forever those last shards of wisdom. The breeze rocking this forlorn wasteland whispers in your ears, “Não resta mais que uma sombra”.