Distinguish Good Pain and Bad Pain

 It's tagged correctly. Simply remember to consult the tags.

 Working out 'hurts' yes, but it's good pain. If you work out too much or too hard, it transitions to bad pain, because you've injured yourself. Notice the different tag on the sensation, then look for that tag on all forms of stress.

 E.g. I like painful ideas. It's all eustress. It's only distress if I'm still clinging to some delusion. It's reliable - I can follow the distress like a scent trail and it will lead to the decomposing idea.

 However, if the vegetables taste bad, don't eat them. Doing homework sucks because it's bad for you. Distress is bad and avoiding it is always good.

 If some distress causes you to avoid future distress, it will stop being distressing. If you really hate vacuuming, but hate having a dusty room even more, then vacuuming will stop being distressing once you've observed the reward. Likewise, if the reward is not worth the stress, it will not only remain stressful, but get more stressful. 

 Many forms of workout are designed to be as distressing as possible. Evil and delusion. I personally enjoy running - the harder, the better. I hate crunches. A study will eventually come out showing you that crunches are bad for you. They're called 'crunch' because they're largely good for breaking things into pieces. However, the honest don't need the study. You can simply look at the stress response. 

 If you can get acceptably healthy with an easy workout, then that's good, not bad. 

 On the flip side, there's folk who think you can avoid all stress, even eustress. These folk are weak and will remain weak. They like to deny that the heights of accomplishment exist or are even possible. If I ever see a counterexample, perhaps I'll remember to post about him.

 

 It's especially important to make the distinction due to individual variation. Maybe, for you, crunches are good. Again, you can't rely on the studies, because they address aggregates, not individuals, and you are not an aggregate.
 

 (This is because doctors can get away with being incompetent. Indeed residency actively drives off competent doctors. They don't have to put up with it, and don't. A real professional knows all the details, including outliers and their signs and portents.)