You can immediately go on to the next portion of the exam if you don’t need a break. However, if you don’t take a break - you don’t save that time for the next section of the exam.
We highly recommend that you take your breaks. You may feel like you can push through, but fatigue has a certain way of catching up to you. Use your breaks to drink, eat, take a rest, use the restroom and to give your mind a break. Pacing yourself is important so you don’t burn out.