I agree, it is impossible to compare people's experiences of pain...or fatigue, since these things are all so subjective. You know how it feels to you, but you can't convey your feelings to another person.
And you have to remember that the perception of pain is 'in your head'. Saying this always provokes a negative reaction because it implies you are just making it up, but that is definitely NOT what I mean! But pain does have an emotional side to it. I'm sure everyone has heard the stories of soldiers getting terrible injuries in a war situation but they don't feel pain at the time, due to the adrenalin rush and the determination to get the job done... And I'm sure we can also relate to the situation where if you are in pain and you concentrate wholly on that pain and think of how awful it is and how it is stopping you doing everything you enjoy, then the pain will seem even worse, you will get depressed about it, that will make the pain worse etc etc. But if you can lose yourself in an activity you enjoy, you stop thinking about the pain for a while and so it 'seems' less painful. This is why things like CBT and meditation are very helpful when dealing with chronic pain.
So pain is very complicated, it is tied up with your emotional state and you will have different levels of tolerance to pain at different times of your life. We can all agree though that pain is unpleasant and it can interfere with people's ability to live a 'normal' life. We all have pain, we all deal with it differently but we should try and be tolerant and supportive of others, whatever their personal circumstances.
Gentle hugs to you all
