This trainer isn't easy. Most days of the week, you'll be asking your muscles and your nervous system to do a lot of work. That kind of strain can be exhausting. That's why it's important to take rest days.
If you're in the "no rest days" club, then having 2-3 per week may be difficult for you. I suggest you let that mindset go and embrace the extra time your body has to recover. If you must exercise, however, do light active recovery like walking or a bike ride. Don't go for a super-challenging hike or play a pick-up game of basketball.
You can use rest days to make up a hypertrophy workout if you didn't have enough time or felt too sore to complete what was prescribed.
Enjoy the days you don't have to spend in the gym. Use the extra time to hang out with friends and family, or do another hobby you enjoy. Strength training and fitness is a lifestyle, but it shouldn't take up your whole life.