Help me with tips to focus clearly during mocks (posting again cause didn't got any answer before)

Idk what it is, but whenever i am practicing anything be it varc,dilr or qa my head is straight, i can see clearly and focus decently, think openly to solve questions. This level of clarity decreases a bit when im giving sectional mocks. But as soon as I start a proper mock test all of that clarity goes out of the window. I can't explain clearly but its like, i am reading whats in front of me, im understanding whats written, but thats it. It gets hard to think upon it and "solve" the questions , this happens mainly in dilr and quants. In varc sometimes i have to read same sentences multiple times. Mind you this barely happens when its not a mock. And when im analyzing that same mock surprisingly everything makes sense, im able to solve those questions.

Another reason im saying all this could be that my today's mock went shit, scored 37 only, in the prev few mocks I've been scoring 65+, so ya that can be the reason as well. (In my defence today's mock was really hard). But still