Because I've been running from doctor to doctor for years without results - because they won't test for anything other than the regular stuff, like blood tests, heart issues, etc. My boss doesn't believe me since CFS or burnout couldn't possibly exist, you just need to focus on your work more. Everytime I say I can't go out since I'm too tired I get made fun of or have eyes rolled at me.

It's like denying someone has a broken arm and gets ridiculed for not wanting to play tennis.