Well i can present u a bit of things which u can do just before ur mock CAT.
When u r sitting in class before a mock test. Notice any dark spot on wall. Now just close both ur eyes and lightly cover them up with both ru hands. Now try to recall that spot ( u can even try to recall whole room in mind..). It will take some time. U can see that spot again and then try again. WHile doin this take deep breaths....N this really helps in concentration and soothes ur eye as well......
P.S.: Next time u see any guy in a mumbai mock cat doin this..u can identify..ITs Me.....ha ha
CHEERS....