To succeed on the IELTS, you must use your time wisely. Many students do not finish at least one module.
As you can see, the time constraints are brutal. To succeed, you must ration your time properly. The reason that time is so critical is that every question counts the same toward your final score. If you run out of time on any passage, the questions that you do not answer will hurt your score far more than earlier questions that you spent extra time on and feel certain are correct.
On the Reading Module, the test is separated into passages. The reason that time is so critical is that 1) every question counts the same toward your final score, and 2) the passages are not in order of difficulty. If you have to rush during the last passage, then you will miss out on answering easier questions correctly.
It is natural to want to pause and figure out the hardest questions, but you must resist the temptation and move quickly.