How can you meditate without something meditate on? You can't chew the cud without cud.
Getting something out of your mind is the point of meditating, at least for me.
It's like I'll be constantly stressing over "how am I going to control x circumstance," which is usually something I have no control over at all.
Then, I'll just sit down and think about it. And think some more. Usually, I'll think about every little facet of the circumstance I'm in, every consequence, etc. And then I come to accept what I'm going through, what could happen as a result of that, and I eventually come to peace with it. And since I've thought about it completely and have come to accept it, it no longer shows up the next day in the form of a panic attack. Because it's "out of my mind" since I've meditated on it.
Hope that clears some things up!