Hi mcwoodhill,
Most silly/little mistakes can be virtually eliminated if you just get in the habit of writing everything down on the pad. Every time you choose to do work 'in your head', you risk making a little mistake. Note-taking doesn't require much time or effort, so you should adjust your practice accordingly and work to take more notes.
As an aside, at the higher scoring levels, the GMAT becomes really 'sensitive' to little mistakes - if you make too many of them, then a 700+ score will become impossible to achieve.
GMAT assassins aren't born, they're made,
Rich