I've done some EMDR. Mine has been "resource development and installation" so I've only had one even remotely negative experience. In general, it's been like replacing traumatic memories with supportive ones. Often it involves my T keeping me safe during violent and awful situations from my past. I can hold on to these images and they sometimes form a safe place for me when it feels like the world is crumbling. Not always, but sometimes. It's hard to describe, so I hope this doesn't sound stupid. We use it off and on rather than as a focus of the therapy. Like a supplement rather than a treatment.