Same for me; general stress makes everything worse but not onlly in the moment when something specific upsets me.
Stress is amazingly bad for your body in every way, not just as relates to endometriosis. I've been rushed to hospital with chest pains that turned out to be stress. It will also make you lose or gain weight unintentionally, make you age faster, make you more susceptable to sickness and pain in general and it will make other pre-existing conditions worse.
While some amount of stress in unavoidable in our lives, trying to minimize chronic stress can really help out with a lot of health issues.
Try hard to set aside a few minutes each day to do something that truly relaxes you; reading, hot bath, meditating etc. I like to sing at the top of my voice :-) Sounds trivial, but it might be the best thing you can do!!
Good luck to you!!
For me, I've found that stress in general makes all of my pain and symptoms worse. But as far as say I'm upset and crying about something at that exact moment do I feel worse pain or cramping... no. But just in general stress seems to make it all worse.