I think that extremes are not good for anyone, and the virtues are extremes.

The opposite of laziness can be tenacity, which is an aggressive motivation or determination. Tenacity can be considered a characteristic like diligence, and may be necessary when a person needs to get difficult tasks done or get through difficult issues. But it can lead to being pushy and overbearing.

It takes a sense of self-worth or resilience to be diligent and carry through a task or life. A tenacious person is diligent and gets through situations, but is more Type A and may go overboard, which may send them in a wrong direction or cause them to make a wrong decision.

An example is a person who works hard and sets a goal to move up in a company. That person may not just depend on hard work to move up, and may look for opportunities to make a promotion happen.

Like all virtues, diligence is meant to show the best effort against its sin, but the best effort is not necessarily the best choice. Moderation plays a key role in maintaining an equilibrium between good and evil, sin and virtue.