Don't dwell on bad shots and don't get too excited by good ones. Consistency is the key to bowling for a high average. They are poor fundamentally and don't make spares or lose their concentration. In order to compete and get better, you must understand that the lanes are changing constantly and that you have to adjust your game to fit. Remember that emotions are not necessarily a bad thing.
Many bowlers rely on the adrenaline rush to bowl good.
You should not make that the only factor in a good bowling game. Keep your cool, if you manage to keep your emotions under control you will see an improvement in your game. You can start to build a better mental game 3 ways. Then try and keep your concentration through all of it. Second, practice separating the game into two halves, the first 5 frames and then the next 5.