Lost one of the twins

I had my scan at 13 weeks.. it's been 4 days now since the tech said there was an unidentical twin but it looked like development stopped at 6.5 weeks and there was no heartbeat.

Honestly.. I don't really know what I'm feeling, this is my first pregnancy, and although I'm happy we have one doing well... everyone kept fussing over me and asking if I was okay. I guess I feel a bit guilty about being happy about the healthy one, but at 6 weeks, I didn't even know I was pregnant so I wasn't even aware of the twin before they died... I keep saying to myself that if my body couldn't handle 2 maybe it was for the best to try give one the best chance but I don't know if I'm just trying to rationalise it away. Does anyone have experience losing a twin, especially at the early stages??