I found out some more information about 守真志満.
I showed a picture of the banner to a friend of mine at work
who is from China and she immediately recognized it as a well known ancient saying. She said it's part of a set of sayings everyone in China has to learn in school when learning to write. She called it wényánwén (文言文) which is "writing in classical Chinese". She said a thousand years ago a lot more meaning was put into the written words or characters, so there is a lot of deap meaning packed into those 4 symbols.
There's a pretty detailed article in the Wikipedia about it here. Here's a small quote from the Wikipedia entry:
"Classical Chinese or Literary Chinese is a traditional style of written Chinese based on the grammar and vocabulary of very old forms of Chinese, making it very different from any modern spoken form of Chinese. Classical Chinese was once used for almost all formal correspondence before the 20th century, not only in China but also in Korea, Vietnam and Japan."
If you've never poked around on the Wikipedia, it's definitely worth a look. It's a free online encyclopedia maintained by the general public. Anyone can edit or contribute to articles. There has been a recent study comparing the Wikipedia to Encyclopedia Britanica - specifically comparing the accuracy of the Wikipedia's articles vs. Britanica - and supposedly they are both equally good.