Racing a half-marathon feels like a little bit of everything. If you have a good level of fitness, the first portion of the race is going to feel almost a little too relaxed. You might start around 70% of maximum effort, or 7.0 RPE. It is tempting to want to push the pace too soon in a half-marathon, but you should stay relaxed through the first few miles.
Once you get to the 5K mark, maintaining race pace is going to take focus and a bit more of a concerted effort. All of a sudden, you might find that sticking to race pace is no longer a 7.0 RPE but is actually closer to 8.0 RPE.
If you are trying to maximize your performance, the last 5K of the half-marathon is going to feel similar to the “comfortably uncomfortable” sensation of the 10K slowly culminating in the “redline” effort the closer you get to the finish line. In other words, you’ll transition from speaking in complete sentences, to just words and finally only grunts and other noises.