The whole idea behind Christianity is that Jesus was a blood sacrifice on behalf of humanity necessitated by the collective sins of mankind. Without going into the weeds of the logic behind it, the long and short is, technically, you can do all of what this Redditor is describing, and as long as you ask God to forgive you, he will. But the reason you don't do it is because self-destructive behavior is self-destructive. Even from a purely secular standpoint, there are many good reasons to not drink yourself into a stupor and go around having sex with strangers.
See, what Christianity and just about all other religions do is they codify morality into mythology. Ancient leaders understood that if you didn't have some kind of fear-based code of ethics, stupid people would just run amok, catching syphilis and getting killed trying to steal their neighbor's chickens. It's difficult to explain "fuck around and find out" to a stupid person because they can't wrap their head around such abstract concepts as "your own actions will cause bad things to happen to you, even if you don't get caught."
If you view the Bible as metaphorical, that's what Hell is. You do stupid shit that feels good in the moment, but the consequences compound and you eventually end up in misery, and it's all your own fault. If you fall into the habit of doing whatever you want without regard for the consequences, you end up doing all kinds of other shit that just gets worse and worse. You make everyone hate you because you lie, cheat, steal, and stink like weed. No one trusts you, no one will help you, and you end up in a gutter or in prison, or you die. This doesn't happen because God is punishing you. It happens because you fucked up your life on your own, and that's regardless of what you believe.
In Christianity, when you turn to Jesus, what you're actually doing is acknowledging that you're a stupid asshole who does dumb shit that pisses off the people around you, and you're pledging to straighten your ass out and fly right before your actions come back to bite you in the ass. Spiritualism aside, that's the function it serves. You're buying into a preexisting moral framework for which the legwork has already been done to figure out what you should or shouldn't do.
Really, it doesn't even have to be Christianity. Just about all religions have rules against promiscuity and unrestricted self-indulgence, and there are reasons for that which go beyond "because God said so".