if it aint broke, dont fix it

If it aint broke, dont fix it is a common idiom which expresses the fact that if something is already working, you should leave it well and not try to change it. Many times people want to constantly change things, people, television shows, whatever it happens to be, because they feel it can be improved upon. However what this phrase is saying is that there is no need to change or fix something already working adequately.