You are not selfish, because there is a limit to how much you can upvote- you can't endlessly upvote everyone on steemit. You wouldn't even have the time. The best strategy is to take a look at the post, and if you like it then upvote. People who don't understand this are the selfish ones because they are only thinking about their posts.
Hmm that's right and i think people on Steemit needs to be grow up because they just want upvote without even Creating a good content for the community.