I personally think selfishness isn't exactly a absence of other people , if we all thought for others in every sense we'd be self destructed a while ago, and if we were all by definition self-serving only we'd be dead as a whole a long while ago aswell. I think to answer your question personally I'd say to be self-interested is not to be selfless in some capacity atleast, because in one setting we eat food to keep ourselves alive (selfish) (instead of just dying out for the animals and other selfless altruistic acts) but other hand we build communities and prioritize entertainment, playing for example ( like video games and such) which inherintly selfish but most of the time people find it better to say play a multiplayer game than solo because a shared experience makes a better memory for most, disregarding what I said though selfish is better long term as you can still prioritize other people for your own reasons .
