keep a firm grip on someone or something
and keep a tight grip on someone or something 1. Lit. to hold on to someone or something tightly. As they approached the edge, Sally kept a firm grip on little Timmy. She kept a tight grip on him. Keep a firm grip on my hand as we cross the street.
2. Fig. to keep someone or something under firm control. The manager keeps a firm grip on all the employees. I try to keep a firm grip on all the accounts.