Funny how many variables come in to play even on the track when you are trying to execute. Also good to analyse what you would do differently and then decide how to simulate that in training.
Anyhow sounds like you are having fun and isn't that last desperate sprint (as in your 800) a real buzz!
Sometimes like a surfer you can tell if the wave is going to be a big one that carries you or one that leaves you stranded after the first lap with nothing left. And mental focus is key. I've heard runners play through a race in their mind and visualize eventualities - that might be a productive exercise for me. But yes, fun, and the buzz a real high point!