First of all, fuck Kant.
Why is his shit so needlessly complicated? A whole world we can't talk about or know anything about? Then how the fuck can he possibly talk about it? What if the world is just exactly the way we see it? Why complicate things even further? Don't tell me I can't get to the chairness of a chair - it's a pretty simply concept, chairness - it's just being a chair. Legs, maybe a cushion, and you sit in it. Can't stop being a chair. Was that so hard?
Look - there are two ways to exist in this world. Chairs just are the way they are, they have being-in-itself. There's nothing special about them. But bros? Oh man, bros are a whole different story. There's no intrinsic broness we all have; we get to make our own shit. Every bro is like a completely blank canvas, devoid of any color, and he gets to paint himself however the fuck he wants. Seriously, this blankness, this void, isn't just any ordinary property; it cuts to the very meaning of what it means to be a bro - a bro exists with being-for-itself, with an incompleteness that he must take care of himself.
Maybe you're thinking, "but Sartre - don't we have a clear description too? Walks around on two legs, usually between five-six and six-eight, hair up top and all that jazz?" Bro, I get it. Nothingness is scary at first. So much room to work, and so little guidance; the thought of nothingness horrifies us. So if you want to take the infinite potential that is that blank canvas and fill it with a physical description of yourself, then fucking be my guest. But you still have to do the work; it's not like you're achieving the certainty of being a chair that way. You're just refusing to face uncertainty; that doesn't make it go away. So my advice to you is man the fuck up, grab some colors, face the future boldly, and just fucking paint.
Don't paint a simple physical description of yourself; don't paint your job, or your stuff. You'll never have the safety of being-in-itself; you're wasting your time trying. Use your imagination; there are other voids with limitless potential. You can imagine what isn't, and that tells you what you are, and what you want to be; make it happen. Who cares if you fuck up here or there? Paint over it. Humanity isn't an 8x10 you get one shot at; nothingness isn't a cup you get to fill once. As time goes on, you'll see more possibilities, acquire new colors, learn new brushstrokes. But you don't get any of that if you don't start painting now. There's a good chance you'll never get it perfect. Whatever, bro. But you can know perfection through its absence; when you look at yourself and say, "almost! What if I just... that's closer, even!" That's how you can discover the truth of beauty - the drive to create is enough.
Of course, while you're out there doing work, you're going to run into other painters, other canvases; don't panic. Why do people always panic? All of a sudden bros act like they're not supposed to be painting, like they're going to get in trouble or something, as if he's supposed to go back to being a canvas when other painters around - what if he's better than me? What if he thinks what I've made myself is dumb? So bros stop painting and let other bros start painting on them, over everything they've created. And do you think other people give a shit about what you come out as? If you let them paint your canvas for you, they'll slap on whatever is convenient for them, and suddenly you're back to being your job, your stuff, how you look; if you let others define you, they will define you out of existence. So don't let them! But more importantly, don't be that asshole.
Again, this shit is easier said than done. Acknowledging the existential void, the vast emptiness of the self, is no small task; for some reason when people hear "You are nothing!" They respond with fear, not hope. We all want to be something, but we don't want to do the work; the temptation to let others do it, or to refuse to do it yourself, is great. Except that no one can actualize your vision better than you, so don't let them.
You know that couple that fucking hates each other, but they can't walk away? I know you know at least one. We all do. What do you think is going on there? They've both given themselves up to the other; he lets her paint his canvas (heh) and vice versa. But of course, they both fucking hate what the other is painting, since they each have a better sense of what they want to be, so they've given up their sense of self and now they resent the other for sucking. She's all like "I wouldn't put blue there, you asshole!" and he's all like, "bitch, that shouldn't be a circle!" but they've forgotten how to paint for themselves, how to face the world, the void, alone. That is the risk you run if you can't face the void alone; that is what you'll become. Who wants that?
We think we want peace and simplicity, which is why we want the safety of being-in-itself, why we tend to paint along the same lines, making small changes and slow improvements. But secretly, we fucking hate peace. We can imagine such greatness, and sometimes we just straight-up get restless. You're not beholden to anyone! If you're suddenly unhappy with what you are, why stay that way? We must not be afraid to start anew, to overthrow what we once were to make what we want; we must never be afraid to change. After all, the goddamn future is coming whether you like it or not; sorry, bro, but the void really is empty; stop pretending otherwise and get to work.
You can get the original Being and Nothingness: A Phenomenological Essay on Ontology from Amazon.