Stress management is much more an art than you might think.
The definition of "an art", is "the expression or application of human creative skill and imagination..." - Oxford Languages.
Some people are better at applying the human creative skill of stress management. You can put two people side-by-side: one is good at the art of stress management, and the other is not. The person that is good at it, will deal with any stressors you apply in the experiment, better than the person that's not.
My point with this is, you need to get better at it. And, how do you get better at it? Education and practice.
Keep learning about stress management, and keep applying techniques. Sooner or later, your techniques and skills evolve, making you better at this art.