How To Balance Exercise And Stress
Let's start off with a cup.

This is your stress cup.
The cup can only handle so much before it overfills and starts to spill. If the cup is spilling your health and life in general, is going to suffer.
Your stressors can be broken down into a few main categories:
Mental
Exercise
Poor diet
Poor sleep

If any of these are taking up too much room, you may be in danger.
This is why it's not always the best idea to go hard in the gym all the time. Exercise, with any sort of intensity, is another stress that the body has to manage and running yourself into the ground when your at high levels can make things worse.
There are 2 ways you can reduce any chance of spillage.
1. Increase the size of the cup
This refers to your ability to handle stress. Meditation, mindfulness, breathing exercises etc. Anything where you can detach your thoughts and emotions from your physical self and see them for what they are; just passing thoughts and emotions.
2. Reduce the stress inside the cup
This is where self-awareness comes into play. Knowing yourself enough to identify when is the best time to train hard and when it's best to back off a little.
Notice how the stressors, as seen in the picture above, can come from anything in life. Work stress, bad diet, poor sleep, the kids having another bloody tantrum and exercise.
There are always going to be things out of your control, but take control of those you can such as improving your diet, prioritising more quality sleep and controlling your exercise exposure.
Creating self awareness
Using a simple sliding scale of stress is an easy way to objectively check in on yourself.
Rate yourself from 1-5 (with 5 being the highest) in these categories:
How stressful was work today?
How were your energy levels?
How was your diet?
How did you sleep?
Do you feel motivated?
Did you rate yourself over 15? You can probably go ahead as usual, but be aware of pushing extremes.
Over 20? Today it's best to take it easy. I'm not saying an off day, but something like a deload session, steady state cardio or an constant mobility session will be a better idea.
Stress has both physical and emotional components that constantly interact with each other. Being aware of where you currently sit will give you an advantage as you continue exercising into the future.
Manage your stress cup before you spill all over the place.