I think of that little voice (the bad one) as the Monkey Brain. It's some totally ancient ghost out of the woodpile that shrieks "OH MY GOD, WE ARE 50 FEET OFF THE GROUND AND GOING THE SPEED OF LIGHT" even as the Thinking Brain is saying "This is a nice pace for a trot!"
I find that breathing helps a lot when that nasty stuff starts kicking up. Deep breathing, regular breathing, counting the breaths 1-2-3-4-5-6 in. 6-5-4-3-2-1 out. That kind of thing. Or yoga breathing, like envisioning your breath coming in and pouring down your body into your feet, sort of thing.
The other thing I find works well against that internal monologue is to focus on something small. Focus on your posting, perhaps. Or ask yourself how quiet you can keep your hands. Or (best, possibly) ask yourself how well you can let your weight relax into your feet. It gives your brain something to focus on other than the Freak Out. AND this approach has the Happy Consequence of improving your riding skills, which makes the ride itself more fun...AND you are racking up time in the saddle, which helps all by itself (but I don't think that time spent in the saddle being anxious about being in the saddle is going to be very helpful).
Best of luck, and I sympathize!
this is good advice. Breathe, focus on form, SING!
Dont' deny fear.
Ask yourself , "What is the worst thing I think may happen?"
Then ask yourself, "What will probably really happen?" you will see a huge gap between the two.
AND , know this: Even if you fall off, it is so totally not the end of the world. You just get up and go on. It's that simple. Really.
Lastly, just to confess, when I ride, and Ive been riding for 11 years, I am always a little bit scared EVERY TIME I GO OUT! I kid you not. When I get off at the end of the ride, there's a little part of me that heaves a big sigth of relief that the worry is over and I get kind of thrilled because ,
well, it's like Elle in "Legally Blonde" when she throws her mortar board cap into the air at Harvard's graduation: "I did it!!!!"