Have you ever been worried about being too selfish? It's an issue that seems to come up a lot and yet, like anything taken to an extreme, it eventually becomes clear that it's impossible to be completely selfless. Even the motivation behind wanting to become selfless is, in itself, selfish. One day it occurred to me that if humans were meant to be purely selfless, we would have given up our bodies to nourish the first predator or bacterial colony we encountered.
But even if you limit the question to human interaction, there is still only so far you can go with selflessness. True, not everything has to be a tit-for-tat interaction. Random acts of kindness, for example, can involve giving to strangers who will never know who exactly did the giving, thus eliminating the risk of someone giving only because they expect something in return.
In fact, with a random act of kindness what you get out of it is that happy feeling for having done a good deed. Wait a minute, you get something out of it?! Doesn't that make it selfish? Can't have that... Alright, so doing an anonymous good deed is selfish too, but so what? What harm is there in that particular selfish motivation? If you think really hard, you can probably come up with some scenarios where a person obsessed with doing good deeds could become delusional and wreak havoc on their community... but first of all, what are the chances of that happening, and second of all, it still seems far less harmful than, say, a serial killer let loose in that same community.
Both the serial killer and the good-deeds-obsessed person have selfish motivations, but the difference is that the serial killer is really bad at managing them. The problem I see with the good-deeds-obsessed person is not that they aren't selfless enough, but that they might not be willing to accept their own selfish motivations. This means that while their good deeds might be much closer to the "purely selfless" ideal than the norm, they might not act as often as they could. They might come up with some idea for a nice thing to do, then think, "Oh no, I have as much to gain from that as I'd be giving, so I can't do that. I'll just wait until I come up with a better idea."
If all a person ever did was anonymous acts of kindness, I'll bet they would still feel like something was missing. Sure, the need for feeling good about your moral integrity might be accounted for, but there are still other needs like safety, food and shelter, human connection, feeling loved and appreciated, having a valued place in the community, etc. My point is that people should pursue their own selfish needs, so long as they put a bit of thought into how they go about it.
It's entirely possible for someone to act on extremely selfish motivations, but do it in such a way as to greatly benefit everyone around them. In other words; mutual benefit. Otherwise, no one would ever have friendships or relationships. True, there are plenty of examples of unhealthy relationships where one person is doing all the giving without getting any support in return, but there are also examples of people that know how to have their needs met while simultaneously providing for other's needs.
So forget about, "How can I be purely selfless?" I think a far more interesting (and practical) question is, "What are some creative and mutually beneficial uses for selfishness?"