It sounds like, overall your first breastfeeding experience was a very succesful one. YOu did a great job, espeically after developing the anxiety.
It is worth knowing that the milk ejection reflex (letdown) is one of those cast iron reflexes in the body that always, always works. What anxiety does is skew our perception - we worry about whether it works, and then start obsessing about it.
In your situation it may have been compounded by having a lowish milk supply which would be normal at that age.
Think of it like this - there is another "letdown" reflex in your body that works - your bladder. When it is full - it can letdown rather quickly and forcefully ie when you are "busting" On the other hand, when it's not so full - the letdown takes longer - eg if you try to "go" before you go out. Anxiety can affect both - but just at the margins. Have you ever been to the dr and unexpectedly the ask for a urine samlple? You sit there, thinking about running water, trying to relax - but it seems to take forever. It's similar with your milk letdown reflex. Anxiety can inhibit it - but not stop it. When your realise it works- always works it takes a load off your mind. You can also teach yourself a few little hints to help you out if it becomes an issue. Some mums find it works best if they are distracted - flick on the TV or read a magazine. Others find they can learn a few little visualisation techniques.
Hope this helps