If at first you don't succeed

Once you decide that something won't work you will give up trying. If you have tried everything you can then you will know for sure it can't work. If you simply tried it one way and gave up then you can not say for sure that it won't work you can only say that you don't know that if you tried it a different way it might work. I am sure you fell the first time you tried to ride a bike but you knew that if you kept trying you would figure it out. If at first you don't succeed try and try again.