If I don't rush a little, often I find myself spending more time than needed on tasks I don't enjoy. Dawdling is bad too. This is a case where variable mental state (due to sleep, other topics on your mind (cf. flow or focus), or ugh fields) can drastically change the rate at which I can do stuff effectively.

If you find yourself making mistakes, absolutely try slowing down. But also try other changes like checklists, different sequences of tasks, or presence techniques (meditation, pomodoro). You might be able to be efficient AND accurate.