Changing to a positive attitude intentionally; "changing my top spin". Originally refering to the rotation spin put on a ball served in tennis to change the forward direction. Similar to spin on pool balls.
It means to take a gamble so that you can change a situation that has become intractable.
You have got stuck in your current strategy. Your current options are either to do nothing or to lose. So you take the third option of introducing some randomness, knowing the situation can’t get worse, hoping the new situation will provide you more options.