on smackdown vs raw 2008(i asking on here because no one goes on 2008)when your fatigue gets high how can you make it go down?

There's always people lurking around the forum so I'm sure someone will respond there. But to answer your question, you need to rest. Among the daily options, you can choose to rest and that'll take some of your fatigue off, but it'll make your popularity go down considerably at the same time.

I did put a thread on smackdown vs raw 2008 on the proper one in may but no one answered

You do R&R, This will make your superstar rest.

but when you do r and r you lose your popularity

Yes but your player needs rest over popularity or he will get injured.