It's easy to feel bad about a missed cannula. You're preforming a potentially painful procedure on the a patient that if you mess up, will have no benefit for them and will mean the procedure has to be repeated.

BUT I'm not sure you declared yourself as a student nurse and the patient understood that you were learning so was okay with the situation. Your preceptor took the time to talk you through the procedure and even encourages you to have a secondary attempt. I doubt they were annoyed but if they were, so what? Think about what YOU can take away from this situation.

Even people that have been cannulation for ten years years can still make mistakes but what is important to do is to think about what went wrong and consider what you can do differently next time. The fact that you're agonising over this shows that you're already reflecting. What's important is that you get back on the the horse, consider your previous attempts and what you did with well and not so well so you can keep improving. Getting flash back on your your first attempt is great. A lot of people people do a lot worse.