There is the general sense that if you look at life, really just look at what's available to your senses and your intellect, you start to get this uncanny feeling that something weird is going on. Events aren't connected. Not every choice you make has a meaningful consequence.
We all seem to be very alone within ourselves, even when we're with other people, we can never really commune with them in a way that's really satisfying. Try looking straight into someone's eyes. If you really stare, what you find is that you can't look straight into their mind/soul/consciousness. Instead you start to notice these layers; you looking at them, them looking at you, you noticing them looking at you, them noticing you noticing them looking at you, you noticing that you've noticed them noticing you looking at them.... Anyway your bodies can touch, your gazes can meet, you can be as close as you want, but you'll always be two separate people trying to make sense of each other.
When you're alone what you notice is that if you look at the objects around you, start to see that these objects hold no inherent meaning.
When you really look at things and try to see them for what they are, you get the sense that the world around you is just this grey muck of indifference. The materials and objects around you don't care about you or your life. Your car won't try to keep working because it likes you, it's just a hunk of metal machined by humans that will run until it doesn't run, and that's that. It won't remember your birthday, it won't wait to break down until a convenient time for you, it will just break when it breaks and that can be any time at all.
But when you look at your car, you don't see a hunk of metal slowly falling back into a state of nature, you see a lot more. That's because the car has meaning to you, meaning which you assign to it yourself. You can be reminded of how excited you were when you first got it, you might think of kissing a pretty girl in the back seat, you might be comforted by the way it smells or be reminded of memories when you see the little scratches on the bumper from that time you hit that sign. Your consciousness assembles the sum of your experience with this car and puts it in a special place in your mind: This car isn't just a thing, it is something to you.
And that's really the trick of it. The person you love is someone to you, and you are someone to them. The person that you are for them is different than the person you are to yourself.
And who are you to yourself?
To yourself, you are something other than what you are. Yes, your identity, too, is assembled by your consciousness as a way of making your experiences and actions continuous and meaningful, not because you are that way on any essential level, but because that's what your brain does. It generates meaning.
What does that imply? Whatever god you prefer is generated by you and whatever community you worship with as a means of experiencing continuity in life and (perhaps vainly) through death. However a person seems to be, in your opinion, is generally not the way they really are, but the way you make sense of their behavior. Your opinions of objects, events, people, and society are all generated by your brain in order to make sense of them in a way that is continuous and comprehensible.
So what does it all mean? Here's where it gets better: it means whatever you want!
You have the power to change your opinions, choose your beliefs, and alter the meaning of your entire world. The old adage is that 'a depressed man lives in a depressed world'. In an existential sense, this is quite literal. The world around you doesn't have an opinion as to whether it ought to be depressed or happy, there are only blades of grass which sway when you blow on them, and a breeze which sways you along with the grass.
And so if you really get into existentialism, your mind becomes a paintbrush, and you can paint over the grey muck with whatever is most pleasing to you. You can make a world that is beautiful, one that is logical, one that smacks of a divine presence, one that is quirky and random, one that is fun, whatever you want!
You might seek to strip away all the irrelevant and invented meanings in your life in the hopes of seeing just how weird, random, and indifferent the world really is. This choice is open to you, but be careful. Your brain is built to generate meaning, and if you try to arrive at some true sense of what the world actually is outside of your version of it, you might get a little freaked.
Instead, maybe listen to a fellow like Camus and try to find a way to make it work for you. Or not, it's your choice after all, and that's the fun!
Original Reddit post by ThisisDangeruss