We use this principle of "tough experiences making us tough" in training. There is a certain amount of validity to this approach. But it can easily turn on you. If the training is too tough, you will be unable to adapt.
In fact...when it comes to training...while what doesn't kill you will might make you stronger. More often that not...it will just beat the hell out you.
I like to think of training much like medication...even though I never take any. It's the same principle. You want the correct dosage so you get the correct response or adaptation. You want just enough to get the proper effect and no more. Take too much and you can have problems worse than if you take too little.
I first saw this "dose-response" terminology used by the brilliant coach who founded Opex Fitness, James Fitzgerald. I really like this outlook because it gets an athlete thinking in terms of getting a certain effect...rather than just pounding away for the sake of pounding away. It's a more sophisticated approach. I'm still working on it.
I encourage you to develop your ability to pay attention in this way. Just don't flail away. Plan proper recovery. Don't overdo. Gently stretch your limits. Cultivate your resiliency bit by bit. Notice how you need only a small dose of hard running to get an adequate response. Notice how you need a much larger dose of genuinely easy aerobic activity to build your aerobic system.
Pay attention to how you feel.
And remember...what doesn't kill you might just kick your butt really bad so that you can't do much for a long time. Be brave...but use good tactics.
At least what I would suggest...