As a rookie golfer, I find it difficult not to get nervous on the first tee when there's a large group of eager golfers waiting for their tee time. The best thing to do is take a few deep breaths and stay calm. If you can repeat a favourite mantra in your head as you're walking up to the tee, even better for relaxing your thoughts. Mine is "smooth as silk" which I repeat as I take my drive. If you flub this first shot, it's important to remain positive and look at the first hole as a practise warm up for the remaining holes.
Negative thoughts are toxic. Positive visualization is beneficial. I've heard that the best golfers visualize each shot. It becomes automatic for them to imagine a positive outcome every time they hit the ball. So the next time you miss the green by a few yards, look at it as a great way to practise chipping. Sometimes I purposely aim for the bunker because I so desperately need to practise my sand wedge. Since my aim is still in the learning stage, I always seem to miss the bunker despite my best efforts! So I'm getting really good at chipping.
It's all good. Just being able to spend a few hours away from working, prepping meals, cleaning house, weeding garden, and doing all the other tedious daily chores is a treat. Happy Golfing!