Make use of an Unsharpen Mask
I’m a sucker for the crisp, anti-aliased, hard edge of the Pencil tool. But, even while working with the tool, some of that sharpness can become lost. That’s where the Unsharpen Mask comes in handy (select Filter> Sharpen>Unsharpen Mask). To reclaim your sharpness set the Amount to between 70 and 80, Radius to 1.1 and Threshold to 0.