In the Second half of your cycle: (Luteal and Menstrual)
Your hormones will start to decrease if you do not conceive. This means you want to really start slowing it down before you hit your period. Your metabolism is up so you can consume more dense foods for energy and nutrients, but as your metabolism increases and hormone levels fall so does the stress on your body internally. Cortisol tends to rise during your luteal phase. More stress from extreme workouts can push you into an imbalance.
This is why you should really prioritize rest during your period and right before it. This does not mean you cannot workout or do anything, just skip the intense sessions and definitely follow the 30 minute rule. Imbalance means stress internally – internal stress means more issues with metabolism over time, which mean less weight and fat loss.
Why no intensity all the time??
When you keep pushing you are getting into a more stressed state physically, when this happens you stimulate the release of cortisol which can potentially harm you if your body is already chronically stressed or have an imbalance. The cortisol is released to help you convert fat into energy after you burn through carbs. When this happens if you are in an imbalanced or chronically stressed state you can end up storing fat as your body thinks it needs to for later or start taxing out your adrenals. Both lead to problems down the road.
A great way to start figuring out when to do what is by figuring out where you are in your cycle. If you are unsure then start with the moon phases, wonky I know but it holds true and is how I had to start after coming off birth control.