Is it normal i still feel guilty for killing my friends reptile?

Its been about half a year since the traumatic incident of loosing my friends Bearded Dragon. It was like her baby & was in my care for a week while her and her partner went away. While she was away, I was constantly updating her on how her little one was doing. Sending pics, asking whether certain foods were okay. I have owned beardies in the past so already have a good knowledge base. In my eyes, I did everything that I could and yet for some reason he died on me :(
The only few things that could have gone wrong, is the fact it was winter & we had a fire going, his terrarium was placed in the lounge. He already had a heat lamp so maybe it got too hot & he wasn't used to it? Maybe I didn't spray him with water enough? Gave him one bath and sprayed him few times. Maybe it should have been more? I was going through a really bad patch of anxiety when I took him under my care so I blame myself still .I just feel so bad because she cried & we are no longer friends ...:(