Well done on a great swim. I hope you have a BOWS (Better OWS) tonight.

The fact that you have had a good swim experience now should make for more in the future. Don't worry if you have panic attacks again though, it does not mean you have lost any confidence, they can happen to anyone. I swam across the english channel and still had a training session where I had to get out as I was convinced there were nasty things in the water. I find singing in my head a great way to stop from focussing on scary things.

If you think that your breathing confidence is an issue perhaps this is an aspect you could really work on in all your training (pool and OWS). Perhaps start with a drill where you increase strokes between breaths and then go back down (ie. 1 lap breath every 2 strokes, then 3, then 4, up to what feels a bit uncomfortable and then down by 1 each lap until back to breathing every 2nd). Apart from forcing you to think about your breathing a lot more you'll be surprised how easy it feels to breath every 2 or 3 stroke when you come down at the end of the set.