Okay this is something every bowler has to deal with and trust me, slumps can last months if not addressed properly. My advice to you is to go and bowl a set and pay no attention to the score. Start by isolating  what you know you are doing right. Start with your form, approach and most importantly balance... balance, balance, balance (Balance is a problem I see with almost 85% of league bowlers...Ever see someone throw a ball and step to the left or right...). Then isolate your release, make sure you are getting the right rotation on the ball, proper ball speed, and correct turn into the pocket. Then lastly, pratice your aim. Make sure you have a target for every spare you leave. If you have an arsenal, bring it all with you. Practice mostly with your #1 ball, then once your game is back, throw some of your other stuff just to watch the reaction. Okay well, that is my formula for getting out of a slump. Surprisingly, for me, it works...LOL... I'm at the point where now I can slump my first game in league and survive because I know what to do to correct myself quickly. Good luck
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They say that 1 in 3 people in this world are ugly. So look to your left and look to your right, if neither one of those people are ugly... Guess who is!!!