Photoshop started lagging suddenly

Hi! I've encountered a problem with my Photoshop program that I can't seem to find an resolution to. I used the program a couple of days ago and it was totally fine, everything worked as usual but now it's lagging every time I use the brush tool. It helped a bit to turn of the ruler with 'ctrl R' but I would like to be able to use the ruler in the future. Does anyone sit on some kind of quick fix? Would be much appreciated! :'))