Musar על פסחים 100:4

Concerning this matter our Sages said : "There is an alert person who receives a reward and there is an alert person who loses by his alertness. There is a lazy man who receives a reward, and there is a lazy one who loses by his laziness. The alert person who receives a reward is one who does his work all week long but does not do any work on the eve of the Sabbath. The alert person who loses by his alertness is one who does work all week long, and also works on the eve of the Sabbath. A lazy person who receives a reward is one who loes not do work all week long and does not do work on the eve of the Sabbath either. A lazy person who loses thereby is one who does not do any work all week, but does work on the eve of the Sabbath" (Pesahim 50b). Observe how the sages came up with the idea that there is an alertness that is good and an alertness that is bad. It is the same with laziness.