Pre-race anxiety can be both harmful and helpful - but there's a sweet spot of nervousness that's useful. If you need to calm your nerves in order to find that sweet spot, follow these tips:

Prepare.
Follow a training plan or join a group whose members share a similar goal. It's also a good idea to test out what foods and drinks do and don't help fuel you. Giving your future self as little to worry about as possible is the key here.

Embrace your pre-race rituals.
Even those rituals that have no apparent usefulness, like wearing those lucky socks or drinking coffee out of a specific mug. It isn't the ritual that's necessarily helpful, but it helps calm your mind, and that's a good enough reason to continue doing them.

Reframe.
The difference between negative anxiety and positive adrenaline is mostly in your head. Turn that nervousness into excitement - it's been proven to reduce anxiety in a threatening situation.

Breathe.
Calming your body can change your mindset. Practicing deep breathing will help calm you down and bring you back into the present when you start to get nervous or tense. Or, listen to a song before your race starts and match your breath while on the course accordingly. Doing this get you into a rythmic breathing and focused state of mind so you're able to tune out everthing else around you.