One of the big motivations for acting like a good person is for other people to notice and think well of that person. Jesus says to do it just for God and to try to hide righteousness from others.
Not only are we supposed to do the right things, we are supposed to do it for the right reasons. Again, this is a very high standard. We can do the right thing for a self-centered reason, and it’s still wrong. This goes above what the Old Testament law required.