@Woodywoodpecker managing Type 1 diabetes can be tough. I am pretty sure we have all been there and all had our "off days". As you say, we "get it".
For me, it help to look at my wins. Think about where I was before diagnosis and weeks later. Then compare that to now.
I went through this with diabetes over 20 years ago but I have done it in the last year when I broke my elbow and was feeling down about how long it was taking to fix and how I was missing my usual hobbies like rock climbing.
I made a mental note of when I could do something for the first time. They were little things like the first time I bent my arm enough to get my hand in a pocket. Then the first time I could bend it enough to fold my arms. Then the first time I scratched my nose. Then the first time I could run my fingers through my hair.
Every time I started to inwardly moan that I couldn't go climbing, I looked back to the days when I could feed myself properly and realised how far I had come. But it was also important for me to realise, the "journey" (sorry, it's not my favourite word but I think it is the right one here) is still continuing. I broke my elbow in August and, on Monday of this week, I climbed a route at the grade I used to manage.
From your threads, I can see that you are improving. It wasn't that long ago when you went out by yourself for the first time, Now you have been on holiday, which, as others have said, is a big thing when so much is different to your daily life.
Diabetes is a pest. I think the only rule it follows is "don't be too predictable"! It took my a long time to stop thinking about mistakes I have made (typically, giving myself too much or too little insulin) but now I don't think of them as mistakes because I am trying to do the full time job of a major human organ whilst living my life. I give myself a pat on the back when I recover from a high or a low because I have learned to do so.
There is no point dwelling on what happened in the past beyond "what would I do differently next time?"
Give yourself a pat of the back for all you have achieved and start planning for your next step with diabetes.
(Sorry if that came across as too much "me me me m". I hope the example illustrated my point without going on too much about me me me.)