Regardless of how quickly you like to work, you must read each question very carefully. Don't read the first few words of the question and presume that the rest follows a familiar pattern. This habit is dangerous.
Skip any question that stumps you and come back to it later. This strategy helps you not waste valuable time.
Many websites and guidebooks offer practice exams. These can be very helpful in your preparations.
For better or worse, SAT and ACT scores have a bearing on you and your college plans. It's not unusual to feel stressed or, perhaps, overwhelmed by the challenges of applying to college; keeping up your grades; and maintaining some sort of balance in life between work and play. Millions of students before you have met these challenges successfully. You, too, can succeed, especially if you don't allow the experience to get you down. Grit your teeth if you must; be cheerful if you can. And good luck!