Growing up, a lot of my generation (I'm smack in the middle of millennials) was taught a certain way to be "nice" that was quite toxic. However, I think there's a split here that doesn't involve going to the other extreme of being mean or self-focused. So let's unpack it.

Explanation of Niceness and its associated Toxicity

So the traditional (mid-90s till now) way of being "nice" is to do things for other people. You hold open the door for them, you help them move heavy things if they need help, you pay for their dinner, you are attentive to their needs, etc. And I think that we can all agree that these are generally objectively "good" things.

However, if you go too far with this, where does that leave the other person's place in your life? If your life revolves around being "nice" to that person, that leaves no room for them to be anything other than a burden to you.

Now you can counter this and say that "well, if everyone is nice, it will all work out." However, now we're getting into the toxic part of niceness, because we have just defined an expectation of reciprocation embedded within the niceness. This is true whether it's explicitly expressed or not - niceness expressed expects niceness returned. If a guy pays for your dinner, whether or not he asks for anything, something is asked from the girl. If you try to fight it, you open yourself up to accusations of taking advantage of someone (quite legitimately, I might add).

If this niceness is somehow continued without reciprocation (which is itself a little bit toxic as explained above), you enter into another level of Hell which is unreciprocated niceness. This can only ever end up with resentment if the person "being" nice cares at all about the relationship, especially when their niceness is inevitably reacted to with hostility by people who can sense the expected reciprocation and the resentment building (a 3rd level of Hell).

Why do good girls like bad guys?

Because good girls are just like good guys in that they like doing things for other people. "Bad guys" are the only ones asking them to do things, which allows them to fulfill that need to help (yes, this even applies to sexual favors - the baggage doesn't fall until later). "Nice guys" are too busy trying to make sure she can't do anything to help him out, and then when they do ask for something they actively undermine its importance (or get really wishy-washy about it) which makes her feel like she can't do anything to help. A "bad boy" will just tell her what he genuinely wants, and as a result he will be genuinely happier when she does it. Any remotely conscientious guy here should recognize how good it makes you feel to genuinely make someone happy. That is what the "bad boy" is offering that you are denying every girl you meet by insisting on being overly self-sacrificially "nice."

Be nice and let people be nice to you explicitly

You don't have to be a bad guy to get out of toxic niceness. Just tell the other person something small that you want that you know they would want to do for you. Also tell them what they do that drains you. Give them space to do something for you.

This works for nonromantic relationships as well. I remember hearing someone say that they would welcome a new person to the neighborhood by asking them for help with something, which gives that person the privilege of helping out and "indebts" them to that person. If you meet with someone repeatedly, you need to factor in room for them to help you. If you're talking about single-time meetings with strangers, then it makes more sense to be more one-dimensionally "nice."

This can obviously be taken too far, but I think the key here is to focus on both sides of favors and balance it between you and the person you like. Don't always try to be the one doing favors for the other, but make the other person feel like you want them there by asking them for stuff. Tell her what your favorite sandwich is. Tell him you want him to go with you shopping. There's no point in lying about it either, because that's only going to make you miserable now and the other person miserable when they figure out that they weren't helping. You can do something positive for the other person both by doing something nice and by giving the other person space to do something for you.

I think girls learn this far easier than guys do just because of how our culture works out. For guys, it's easy to fall into the trap of thinking that we need to be over-the-top "nice" in order to get the girl, to the point that we shut out her sense of self-worth in the relationship.

Thoughts?

TL;DR:

Being nice can be toxic because it doesn't leave room for the other person to feel wanted. Bad boys make good girls feel wanted. Make the other person feel wanted by telling them what you want even if it feels selfish. It's not selfish. In fact it's selfish not to.