Man, i remember those feelings! It took me a while to shake the nerves, and more important how to deal with not acheiving the goal-300. So i worked with my coach at the time and came up with a gameplan. I still use it to this day. If you let your mind wonder and think about the 300 right now you are putting yourself at a disadvantage like i did back then.
First, get a pre-shot routine thats comfortable and stick to it. Make sure you do the same thing everytime, this will make you more comfortable in those high pressure situations. Wipe your ball off, dry your hands, whatever you do before you set up, repeat it every time.
Second, and what i feel is the most important is use Key words before or during your setup just before starting the approach. Different situations call for different Key words for me, but normally during high pressure situations mine are Relax, and Be Smooth. Saying these words takes my attention off of the situation, because i focus on relaxing and being smooth rather than saying i need this one for 300. And ill say these during my approach if i have to, just to take my mind off need 3 for 300, whatever. Main thing is connect it with your tendancies, but never make them something like Dont pull this shot, Dont choke etc. Make them positive, you will be surprised at how your brain reacts to positive thoughts in those situations.
Third, i learned to put myself in those pressure situations through practice. Every game of practice i always try to use the 9th and tenth frames to go ahead and "pretend" that im on 300, or that i need 3 strikes to shoot 800. I'll even do that in league, even if we are winning and im not needing it at all. The point is to get used to those situations, so that the stress level is at least lower than normal. Using this practice time combined with the key words will get you there faster than just waiting for the chance for another 300.
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Taking your lunch money, one strike at a time....
