Join Date: Oct 2013
Location: I'm an American girl living in southwest France
I'm a beginner too, so maybe listen to other people before you listen to me, but here's my 2 cents.
First of all, it's impossible to not panic in a situation like that as a beginner. You can tell yourself all day long tomorrow you will not panic again, but I guarantee you will. Panic is a natural reaction to being over your head. Don't beat yourself up over that, and don't expect to be able to just will it away.
Take lessons. When you gain confidence in your riding, you will be in a better position to deal with unexpected situations and you will therefore panic less and less when crazy things happen. After taking lessons for a few months, my lesson horse went berserk on me during a lesson for almost 30 minutes straight, over and over freaking out over something he kept seeing in the corner of the riding ring. If this had happened in the beginning of my learning, I would have been dumped, plain and simple. But since I have a decent seat and some skills I've learned, I held on and calmed him down and then worked him through that spooking stuff until he finally chilled out. It was dark, it was cold, it was windy, and it was scary as hell, but I did it - by the grace of my lessons! I never could have done it without the learning in place first. No one could. [Turns out, it was a piece of purple-painted wood in the grass near the riding ring that was freaking him out. He is such a creature of habit. Any little thing wrong in his world is a leopard trying to kill him.]
Go on youtube and find training videos on natural horsemanship, unless you can afford to buy them from Clinton Anderson or Parelli or even Sean Patrick. There are tons of free videos from others, both professional and amateur. Do a bunch of groundwork with your horse so he feels more confident in you as a leader. It should lessen those instances of him freaking out and it should make him more likely to listen to you when you say "whoa".
Congrats on getting back up on the horse. I hope you're wearing a helmet. If you're not, please get one. I know they don't look cool in western riding, but your brain is your most important asset and more horseman die or are permanently injured by head trauma than any other thing.