I think the best tool for regulating emotions (fear, anxiety (which is closer to excitement), excitement, anger, etc..) would be mindfulness meditation/awareness.
A lot of it is perspective, but it takes practice to be aware of when emotions arise up.
This is a big thing for 99% (hyperbolizing a bit here) of people who struggle with what they call mental game. Perspective is a big thing. It's also a simple thing.
Sounds like how I play par-3s!
But really, the idea of hitting two shots on a par-5 and then mentally treating the rest as a par-3 helps me a lot, especially since I pretty much can't reach in two. But I can hit two good shots to leave me a relatively easy par-3: I think about where I want the "tee shot" to be from and strive to make it the shortest possible par-3. At my home course, two good shots on the first and last par-5s leave me with manageable 60-80 yard par-3s; a good drive or a good fairway wood can make that even shorter.