There should be days, sometimes even a few in a row where you don't strength train.
Your body needs rest and the regeneration that comes with it.
So what can you do on these off days?
A walk is great. Easy on the body and helps keep the blood flowing to those muscles that need repair to grow. Walk at least 45 minutes at a steady pace, but pause to enjoy the scenery. Drink water to stay hydrated, especially if the temperatures are high.
Stretch. A good stretch is relaxing and helps to maintain your body tone. Start with basic YOGA stretches to warm up the back and abs. Go slow and enjoy the sensation.
If you cam get into a yoga class on your off days that would be helpful.
Do light body weight exercise. A few push ups or some ab work can be good, but not if you just did that with weights the day before. The muscles need rest.
Enjoy you rest and make good use of the time. This is very helpful and will bring you back to the weights ready for more.