Sometimes Taking Your Run to the Flats is Necessary
If you want the most out of each session, then start looking at your swims, bikes and runs as "training" and not just a workout. The most essential element to any training session is to develop and train movement patterns we want to come out on race day.
Here's what I did to modify my hilly run so that I could still train the patterns I want to develop. Making little changes like this once in awhile can really help you get the most out of each session.