by this time i thought i could n't take any more ; i began to think i was going mad , i 'd been through several weeks of manic exertion , taken enough speed to kill me , and i began to have a recurring phobia about knives every time i saw a knife , i could feel it and see it cutting throats , wrists , balls when sonia and her son crispin had been helping to varnish the floor , i had told him he could come and watch the minds practise .