Photoshop is very slow, or 'laggy'

So when I use Photoshop, it lags so much. When I move the cursor down the tool bar, the tools box's glow after already being passed. When I move the actual Photoshop window, it moves and stops and then moves and stops. When I draw with the paint tool it does the same thing: moves and stops, moves and stops.

If it helps at all, when I opened the performance window to change stuff, I noticed that the problems were gone. Don't know what that means, but it is really weird. I open the performance window, and the tools glow when they should and (while i can't actually do anything) it seems to work.

Please help